VTA on the fly

Perhaps he had no idea of "the advantages of VTA on the fly", but your story as told doesn't prove that, if you made your adjustment surreptitiously.  Do you know approximately how far the pivot moves when you make a half turn adjustment of VTA?  Every one of my 8 or so tonearms has the capability for VTA on the fly, but I would never think of adjusting VTA "on the fly".  I lift the tonearm, make the adjustment, and then drop the tonearm, using the cueing device.

While the record was playing I turned the micrometer one half turn clockwise, and there was according to him the right amount of bass. He then asked me what I did, because he seemed startled, and had no idea.

That's the way I did it with my Graham 2.2 and Conqueror arms. No point stopping when it works smooth like its supposed to. A lot of audiophiles have no idea. I mean of what it sounds like. A lot know the concept of VTA, but hardly any have much experience hearing it. I used to fine tune VTA on every record and write it on the sleeve. Until the Koetsu. With the Black Goldline I could still hear and fine tune it, but unlike the Benzes with the Koetsu it sounded so good it just seemed superfluous. 

My systems improved so much since then you've just made me curious to see if that's still the case. 

The other thing I'm curious to know: clockwise, was that lowering the arm down? 

VTA-on-the-fly is a handy feature, but it’s no magic bullet for phono cartridge setup. That’s because when you change VTA/SRA, you also change VTF and - more importantly - overhang. So if your overhang was correct before adjusting VTA, it will be off by some slight amount after altering VTA.

Some audiophiles in this forum argue that phono cartridge alignment is not critical and that these small changes are of no consequence. I suspect that their systems simply lack the resolution to reveal these changes, and it’s most likely that their turntables are not properly setup.

Or the change in VTF and overhang are so miniscule, when you turn the micrometer typically used to alter VTA on an "on the fly" tonearm by only 180 degrees, as to be inaudible even to a pair of Golden Ears such as your own.  I actually doubt that a half turn could make any important audible difference in bass response, but I wasn't in the room.