Could Class D really be that good?

Sorry, wrong.  You have no idea what is producing those different numbers.  You just want to believe in something.  Those Wima Polyester caps that they use (both Fosi and Ayima now use the in all their latest gear) are crap.  I replace them with modified Wima polyprop caps that are oriented so the outside foil is to ground.  The Ayima Max and all the latest Fosi and Ayima amps all use the same inductors and capacitors yet still measure different.  Lots of things in the design can influence the measurements.  Fosi is now adding feedback around the output coil and this lowers the distortion and makes it less load variant (ie....measures flat at 8 ohms and 4 ohms).  The only way to know if a single component (or several) changes the sound and or measurement is to use the same amp and just change the parts.  Then you will actually KNOW something.

I have NEVER in my entire life heard of any high end audio designer, engineer, manufacturer say this

Hm. Not been around, apparently.

The only way to know if a single component (or several) changes the sound and or measurement is to use the same amp and just change the parts.

Wait- what? So if you change parts it does change the measurements?

Boy you just keep sawing on that limb.......you cannot say anything but the same thing over and over and you know you are wrong and cannot prove otherwise. You alone hold your opinion. I have been around since 1975 and in the industry since then. I did not say it changed the measurements.....but if you are going to look for a different measurement than that is the way you would do it......using one amp or device.

Please prove you are correct. Show us the measurements......You know you cannot or you would have done so by now. You know you are wrong and just keep saying you are right. Would you rather be LOVING or RIGHT. Some would rather be dead right then ever admit that they were wrong. Are you one of them?

You are not your thoughts....you are not your opinion. You are infinite love and joy....and always will be....forever and ever. You can let go of your opinions because next life you won’t even remember them....you will obsessed with something else you need to let go of....he he.

When you really truly love yourself at your core.....you cannot do or say anything that is not in harmony with your soul.....you speak truth. Please love yourself more. I would love you to be more happy. Having pretend opinions...to be right...is not happy creating. Growing up and admitting you are wrong is the hardest thing to do. We are all so stubborn (me too). It is so easy to be bad......to be righteous......it is hard to be loving. It takes great courage to be loving. For we fear rejection....as we reject ourselves. Look in the mirror when you first get up in the morning and smile at yourself and tell yourself out loud that you love yourself and are beautiful. Do this several times every day.....Caress your face like your mother did when you were a baby. I do it when I drive. Wave at people. Tell people how beautiful they are and thank them for sharing their light with the world. Treat yourself and everyone as if they/you are your pet or baby. This is the way to really start to feel love for yourself. There is just God loving itself. You are your mother....the mother of all.....loving your self and everyone. Forever. This is the truth of your soul. Bless everyone.....forever.

Alright, it is fun discussion but counter-productive (to me) talking these technical issues phyosophically.  Call me stuborn but, before making any major purchase / investment, I would like to see positive / superior objective measurements on the particular model I intend to purchase to get the maximal bang for the buck.  I will also do my due diligence to get the users' and revierers' (I thrust) feedback and get a feel how it sounds.  I won't make my decision just based on diyers claiming that all Purifi / Hypex based modules (including power supply) measured the same.  Different implementation in the input buffer makes significant difference!  And that is true!

I don't think you are subborn.  You are just checking out all possibilities.  However, ASR themselves say that super low distortion is not required for "perfect sound"  Only a certain measurement of SINAD is needed.  They like lower measurments but they never claim they sound better....because they believe everything that measures below their SINAD value is perfectly transparent.

It is not just the input stage that changes the sound in a Pufifi amp build.....it is the damping of parts and the input board.....the cables, the AC inlet, the output connectors, the quality of parts on the input board. etc. to infinity.  I modify the Sparko regulators and the Sparko pro op amps for better sound.  I modifiy the ouput filter caps on the Purifi boards by removing all 6 on each board and removing the distortion producing steel leads and soldering 6N copper leads using Wonder Solder.  I then test the caps for outside foil and put them all back in so the outside foil is to ground on all the caps.  This makes a noticeable sonic improvement......and no, I bet you cannot measure it.  Look at the reviews of the NAD Purifi amp and my modded Purifi amp on 10 Audio.......he says my amp is way better and even with the mods it is cheaper than the NAD.  This game is infinite......just like our own nature. Eveything makes a difference and most things that make a sonic improvement cannot be measured.