Did more troubleshooting and determined that the issue is not related directly to Retroarch, but posting my findings here in case others are running into the issue.
The issue seems to be caused when sound is active in some way, and then is switched over to Intel Display Audio while it’s active. In that case, somehow Intel Display Audio stops working. It seems to reproduce reliably when I do this, e.g.if I turn off the TV and back on while sound is playing, or if I pull out the HDMI cable and plug it back in while sound is playing. If sound is not playing it is fine, but if it is, it seems to mess things up.
This seems consistent with the behavior in retroarch only causing an issue when a game has been started, but not otherwise. Presumably exiting retroarch may temporarily trigger sound to go back to the main sound driver, and then back to the intel audio driver - perhaps due to the resolution change of the full screen or some other such reason.
Anyway, since I can reliably reproduce it outside of retroarch, I’m convinced that while retroarch may be triggering the issue, it is not the cause of the issue, and so it’s not an issue for the retroarch team to solve.