Class D

The 1200AS 2 is still the current Class-D module from ICEPower, what have you been sniffing.
https://ibb.co/vvwzGV5
https://icepower.dk/products/amplifier-power-modules/as-series/

Nothing but air. However if you are suggesting that this amplifier is representative of all class D amps you would be committing an excellent example of the logical fallacy known as Guilt By Association, and it works like this: 'Because this particular amplifier has significant phase shift at 20KHz and is class D, therefore all class D amps have significant phase shift at 20KHz.'  Because its a logical fallacy, this idea is false.

Obviously ICEPower has chosen a different set of parameters for what they feel is important, which with a short look at their website, appears to be public address. At any rate there are class D amplifiers that have less than 1 degree of phase shift at 20KHz.

OK George- that one is debunked. Please proceed to the next.

However if you are suggesting that this amplifier is representative of all class D

No I defiantly don’t sunshine, but as you said

"Decades behind"!!!!

Decades! Really! It is also not that either, again just furphy from someone in product protection mode.

As you say you’ll get around that problem with "global feedback", you can throw all the "global feedback" you want at it, to fix the phase shift problem.
Every one knows "global feedback" is not a good thing in any amp, it’s a "sound sterilizer" and should only be used very sparingly if possible, just to clean things up a little, and preferably use only "local feedback".
Which won’t help your plight as you’ll need a stack of "global "feedback" that has to incorporate even the speaker output filter into it, to try to remedy this kind of phase shift problem down to 1khz 40 degrees out of phase, and 70 degrees!! at 10khz (in red). https://ibb.co/vvwzGV5

And to those many that complain about it, this is why you have this concern with Class-D sound in the upper/mids and highs. And a 1.5mhz switching frequency goes a long way to remedy it (without throwing stacks of feedback at it), like they used in the 55kg $KKKKK Technics SE-R1, and hopefully next month in the far more obtainable and affordable SU-R1000 integrated.

Cheers George

I've seen that graph on other forums it's the amplifier phase which will be run through feedback. What's the reason for posting it?

No, what's more amazing, is how much of a troll you are, and that's been expressed by many here on Audiogon more knowledgeable it seems than you.