[_-___________-_]

> Also, if you dive into the Windows 10 sound settings, you can set the default device and the volume for every application and it'll never deviate from that unless you explicitly change it again.

Yes, I've dug deep in the Windows 10 sound settings many times. I promise you, it regularly deviates from it, in ways that don't seem at all deterministic. Your solid belief in Windows 10's sound system not containing any bugs doesn't jibe with my experience of it :)

As mentioned in my previous comment, I suspect there's something other than PulseAudio causing your issues, like some external tool (possibly bundled as part of a desktop environment) trying to manage the sources/sinks/volume. Because of that hunch I'd probably suggest your distribution's bug tracker as the appropriate place to report the issue, as it's likely an issue of integration.