According to the Apple Store, bug fixes and performance updates.

If I had a PC, I’d be testing to see if it fixed the volume changing of grouped rooms behavior, but that’s merely a guess. 

I will wait to see if anyone has tried it I think 

14.18.2 suggests it’s merely an iOS app update. Probably released in order to fix the group volume issue.

Not just iOS, my Android phone also had the update. Just the app though and not the speakers.

Thanks all I needed to know app updates do not futz thing's up usually

Just updated and it didn’t fix the volume slider issue 🤬🤬

In my experience fixes take at least 2 and normally 3 releases to be resolved. This was true of the Move issues and the recent ARC bass issues.