Why do you guys pursue a flat frequency response when you buy a subwoofer?

And in the spirit of good will Duke, because you are indeed a gentleman- I would change “ myth “ to vague assertion.

best to you in these crazy times....

There's always a different way to reply. Could be he was so enamored with the alliteration and proud of coming up with Miller's myth he just had to use it even though it had nothing to do with anything I'd said. Could have asked about that a lot of different ways. I'm not comfortable having people, since you don't like lie let's say make things up about me. That's a misperception he had the opportunity to correct, and he chose to double down on the insults. Not exactly comfortable with that either. Mainly though I'm far from thinking it had anything to do with misperception. I think he perceived what I said just fine. But rather than dealing with the substance of what I actually said he thought it better to belittle it as myth. That's my perception. If its wrong, he's free to clear it up. I'm certainly open to that.

Ahh... Well there was nothing vague. And the assertion was never made. But "in the spirit of goodwill" it'll do.

@tomic601 , @audiokinesis @erik_squires

A lot of stuff you guys mention are steps i’ve already gone through over the ages. Both my rooms are treated with bass traps, absorption (ceiling, FR) and diffusion panels.
Room 1 has 5.2 Elac Adante speakers and HSU subs powered by a Yamaha RX-A3080 (active bass management and all the frills on this Yamaha’s flagship made it easier for me) Preouts go to a Jungson 80W/ch class A chifi amp. I’ve gone the full 9 yards with REW, subcrawls, positioning, treatments and EQ to get fairly flat curves. I have a 2nd pair of Tekton Moab speakers as a standalone 2.0 system with the Jungson amp in this room (No subs, so it leaves the discussion). I listen to music 95% in either 4.2 or 5.2 and movies 5% in this setup. It works really well for me when i’m listening to surround mixes, movie/game composers (a genre i really like with orchestral elements tied to electronica), electronica, house, trance, etc

Room2 was a nightmare that lasted months of tinkering. It is a 2.2 music setup with no bass management. 2 Yamaha Ns-F901s and Rythmik subs powered by a Yamaha A-S2100 integrated amp and Denafrips venus DAC. I use this room for several other genres of music. It took me a while to get these subs "blended in" as best as i could. I did the phase matching with the sub’s continuous phase adjustment feature with knowledge of both the sub and the speaker’s phase response (i measured it) at the crossover point. I crawled all over the place and the subs had to be located in a non-aesthetically pleasing position to sound right. I listen to many different genres of music a.k.a i’m not listening to 1 track over and over. They are not all recorded the same. If a recording’s off from a band i like, i am back to tweak OCD again.

My perception is that subs are made to cater mainly to the Hometheater market (set the crossover on the receiver and the movie explosions go boom boom boom all day long!! easy as pie!). But, it seems to be much harder if you’re a music aficionado. My perception is that these manufacturers leave dudes who are music aficionados out in the cold. A competent speaker designer like..say Andrew Jones, for instance, has so many variables available to him when he’s designing drivers, cabinet, crossovers, blending them, etc. He comes out with a wholesome design in the end.

Now, when subs are being integrated with these speakers, the sub appears to be an afterthought. A end user like myself who’s not a speaker designer or professional audio engineer, is somehow being asked by sub manufacturers to make it all work together/figure it out somehow. They release a flat curve to make themselves look good and sell a product. At the end, its a customer like myself who has to go to enormous lengths and months of tinkering and treatment to make it all work right. I may have very few variables to work with actually (than what a speaker designer may have available when he’s designing something from the ground up). Let’s see, a sub volume control and a crossover if my amp doesn’t have bass management, that’s it. To my knowledge, only Rythmik even offers a phase control that’s more than just a 0-180 flip switch. The rest is...crawl around, throw a bass trap, etc and make it work somehow...

Is my perception right or wrong gentlemen?

I don't. It may be easier to start with a speaker that is reasonably flat but a speaker that is flat will sound bright and bass shy under most circumstances. Most people have no idea what their system is doing and their opinion is based on assumptions that are usually dead wrong.
My system is measured and graphed on a computer. Filters are generated that make the systems performance perfectly flat as a starting point. Then response curves of my design are overlaid to make the system do what I want. The basic curve is boosted 6 dB at 20 Hz and down 12 dB at 20 kHz. On top of this there is dynamic loudness compensation which follows the Fletcher Munson curves based on volume. This assures that the tonal balance I like in my room is the same regardless of volume. After this is the subwoofer crossover which I can modify on the fly if I desire. 
The problem is that the right tonal balance changes with volume. In a standard set up each record or file has a "right" volume. A record that was mastered for high volume will sound dull and bassless at low levels prompting the listener to think it was a bad recording. Records that were mastered for lower volumes will be shrill at higher volumes making all the women in the room extremely angry. Tone controls help a little. But they and standard loudness compensation are just not l flexible enough on top of the fact that the listener really has no idea what is going on. When you see what your system is doing on the computer and integrate that to what you are hearing you learn pretty quick what making specific changes will do. This is an aid of immeasurable benefit. This alone justifies digital audio to the point where I gladly digitize my phono amp so it can play on the same ball field. 
I have measured several systems. The reason Wilson's are so... comfortable is that they are engineered with a notch at about 3 kHz which takes the sting out of female voices and violins. I suspect other companies do this as well.