In fact this bug is a problem at wireplumber, not at pipewire-pulse.
Program wireplumber uses config-file /usr/share/alsa-card-profile/mixer/paths/analog-output-speaker.conf .Like at pulseaudio the problem can be solved by commenting out thye next lines:
; Make sure the internal speakers are not auto-muted once the system has speakers [Element Auto-Mute Mode] enumeration = select [Option Auto-Mute Mode:Disabled] name = analog-output-speaker
