copying pipewire-pulse.conf to ~/.config/pipewire/pipewire-pulse.conf.d disables pipewire-pulse
I created ~/.config/pipewire/pipewire-pulse.conf.d and copied /usr/share/pipewire/pipewire-pulse.conf into it.
This stopped pulseaudio working. Running pactl info produces the message:
Connection failure: Connection refused pa_context_connect() failed: Connection refused
This is reversed by deleting the file, so I suspect it's just not supposed to be copied to that directory but it seems like an ambiguity in what config setup is allowed, and it's not clear why that breaks.