Specifically it needs a supply that offers 5V/5A as a basic profile outside of PPS (programmable power supply), because the Pi doesn't support PPS negotiations.

Specifically it needs a supply that offers 5V/5A as a basic profile outside of PPS (programmable power supply), because the Pi doesn't support PPS negotiations. That is what's so rare, much more than the actual ability to do 5V/5A.