This depends on what dormant means, I think. Dormant audio can mean:
1. Steady stream of 0s.
2. Pausing (corking in pulse-speak) the stream.
3. Closing the stream entirely.
We know option 3 has not been taken. We can try to determine if 1 or 2 with the output of `pactl list` while the system is idle.
I'm not at my laptop so I can't check if we have it by default (we should), but do you have suspend-on-idle module enabled? This information should appear in the pactl list output.
IIRC, suspension cannot happen as long as any stream is connected, even when corked.