Regarding the change to the gain filter, which now also controls the left and right speaker balance, I imagine it means keeping the two filters separate, to maintain compatibility with all versions and not affect saved customizations.
Turn it off if you do not like it: Settings > Timeline > Adjust Clip Gain/Volume
It is about controlling which channels are affected and less about balance. If you work in 5.1 audio, then you definitely want the option to adjust only the subwoofer or center channels.