I wonder, problems with PA emulating ALSA were AFAIK always blamed on apps abusing ALSA APIs. Does Pipewire do a better job of emulating ALSA than PA did, or does Pipewire just rely on the fixes installed to make those ALSA apps start to work OK on PA?
I'm not familiar with the details of this topic, sorry. I believe PA did (or still does) publish guidelines for a 'safe' subset of the ALSA API.
Don't know if Pipewire has published something similar, but I would guess there are corner cases in the ALSA API that wouldn't work well on top of Pipewire. E.g. the buffer rewinding, considering that Pipewire is explicitly designed around never doing that.