@ricevs , it would probably be best not to post links to technical articles you do not fully understand. I was trying to be nice before and give you a way out. Class-D and PWM are not the same thing. A Class-D amplifier may use PWM. However, that is not what you said, you said this,
"The GaN1 is the DAC.....it changes PCM directly to PWM (class D analog switching)".
Class-D may use PWM, but PWM is not Class-D. Put in simpler terms, an Orange is a fruit, but not all fruits are Oranges.
Class-D is an amplifier architecture. Peachtree may call it Digital Class-D, but that is marketing. There is no such thing as "Digital Class-D". You are more accurate to call it a power DAC as you did because that is what it is. They call it an amplifier but it does not amplify anything hence why it cannot be a "Class-D" amplifier.
Did you measure the switching frequency on your oscilloscope? I was curious as to what it was.