I’m a ham radio operator and it generated RFI which was picked up by my transceiver. Went back to class A/B and now no noise.
You can check this yourself, get a portable "am radio" tune it around between 500-700khz "unmuted" turn up the volume, and go near your Class-D amps speaker terminals with it and even switchmode wall warts, and listen to it scream.
This is "what it looks like" on Stereophiles oscilloscope square wave shot (top pic) https://ibb.co/xgHv8dZ
But now Stereophile don’t show that pic anymore and filter it out with their AP test gear filters so you don’t see it, which should not be allowed, in my books as it's not representative of what comes out the amps speaker output.
They say it’s because the noise overloads the AP gear, but that’s bs because they didn’t use it years ago, with the same gear, and if it does then they should fix it not hide it.
Cheers George