bug/limitation of sndiod

According to faq13, I now have a machine configured with

# rcctl set sndiod flags -f rsnd/0 -F rsnd/1

It doesn't work "symetrically", namely if I start playing something
with mpv while the USB audio is plugged in (pleasantly surprised:
it's the USB-B input from my panasonic hi-fi system and it works
like a charm), and I unplug the cable/turn off the appliance, it
reverts to the internal azalia audio.

BUT if I plug it back in, uaudio reappears in the dmesg, but somehow,
sndiod doesn't jump back up to the USB output.

I have to quit mpv and start it again for it to output to USB.

Is this fixable ?

-- 
	Marc