Any way have pc be a bluetooth audio sink on Pipewire?

Yes you can, by default with wireplumber you should only have to pair your bluetooth device with your pc and you should see your device in pavucontrol settings

I just tried and didn’t have to do anything, just paired my phone over bluetooth and started music, it came out of the monitor

It should be pretty much the same as your link

Tell me if it doesn’t work we’ll try to troubleshoot this.