Just got this phone today and after connecting it to my bluetooth headphones, I noticed that the sound bar keeps showing up whenever I do anything while they're connected. I could even be browsing Reddit and it will show up at the top of my screen for a few seconds every time I tap a photo. It also seems to reset the volume back to it's original setting each time as well.
It's definitely true that the apps I use can access the audio but the fact that it pops up every single time for every single thing seems excessive. I would search for apps in the Play Store and it would pop up for every search and when I looked at every app. If I'm playing music it stays hidden, though.