ZDoom

That is... logical.

The point here is that 'stopmus' must clear the active music. And once it's cleared, even a snd_reset shouldn't restart it - because there was no music playing at the time of reset.

One could argue that calling snd_reset CCMD isn't automatic but intentional, but it doesn't matter anymore as music restart can also be achieved with 'changemus *'.

Of course this was intentional. That was the whole point of this change. If the music was explicitly stopped it should not automatically resume.

I've noticed that newest beta Zandronum builds (which are based off ZDoom 2.8) no longer restart level music on snd_reset CCMD when it was first stopped with stopmus CCMD. I've found this commit that seems to introduce the change:
https://github.com/rheit/zdoom/commit/a2c975bf30d6b48ecffb8a67ffbc1a9ab452d302

Was this side effect intentional? The commit message only states that this was supposed to affect volume changes in the menu.