This sort of context-aware volume control is fairly common though, right? If you adjust the volume while you're on a call, it's adjusting the phone volume. If you adjust the volume with the door open, you're adjusting the door-open volume, but it'll persist to when the door is shut (so, regular media volume) for the duration, which isn't the worst case.

That being said, I get what you mean and why this would be frustrating. I've also had a call end and been absolutely ROCKED by how loud the underlying music had been because I forgot I had it set that high and the call obviously wasn't that loud.