Can't switch input to "Monitor of Built-in Audio Analog Stereo" via pavucontrol with wireplumber, but with pipewire-media-session it works fine

I use Fedora 35 KDE beta. In Fedora 35, wireplumber is the default for pipewire. I notice I can't switch input to "Monitor of Built-in Audio Analog Stereo" via pavucontrol with wireplumber, the "Set as fallback" button does nothing. After removing wireplumber and replacing with pipewire-media-session it works fine.

Pipewire version is pipewire-0.3.37-1.fc35

Wireplumber version is 0.4.2-1.fc35