Yep same here too. Suggest everyone make sure they report it as a bug using the Apple online bug reporting tool.
The worse part is when you actually HAVE music playing through your HomePod when you go to restart your iPhone - considering you have to hold the lock and VOLUME UP buttons at the same time, then your iPhone's off and you now have no way of turning down your incredibly loud music if you're not within earshot of the HomePod (say, if you're in bed and it's the middle of the night and the HomePod is in the lounge......... and you have neighbours........
I was in bed and the volume buttons weren't working. Thought it was this problem, so I started the music downstairs on low volume (just enough to faintly hear the base) and started using the volume buttons to double check they were actually working, just for the wrong device. Then I tried restarting my iPhone and suddenly had to RUN downstairs.
Please fix this Apple! Pretty crippling bug.