As a lowly European who doesn't have a PS5 yet (and probably won't be able to get one on release either): Does 3D audio through headphones work if those headphones are plugged into a receiver? The FAQs about this seem to indicate it only works if the headphones are plugged into either the controller or into the console through USB. Seems like technically it should be able to work through a receiver as well, because in the end it's just processed stereo audio, but does it?
I think the headphone stipulation was just a roundabout way of saying it doesn't work through bluetooth (Or any audio to headphones for that matter). I think it will still just be sent out as LPCM after its been processed by the tempest engine, so should be fine dropping off the audio in an amplifier as you say.
Nothing confirmed though so we'll have to wait and see for definite confirmation.
edit - wait, hang on though, the Dualsense controller is wireless, is it confirmed bluetooth or is it proprietary wireless stuff? If its bluetooth then I still think it was a way of saying you can't connect BT headphones direct to the PS5 but maybe means it can even encode regular PCM (which is compressed, so can go down a regular old ARC and eARC or amplifier interconnect isn't needed) with the tempest engine magic-jambo. As BT audio definitely doesn't support an LPCM-like quality signal.