Shared initiative does answer some of the little niggles that sometimes come up in actual table-top - "we're on the same initiative, so can't we both move up to the boss at the same time, and then both benefit from the other being there, for our sneak attacks?" Realistically yes, formally no, and the tabletop has ways to work around this, but they aren't perfect and the players can often come out getting less value for their turns than they feel they should have been able to.
BG3's shared initiative does address this - but it comes with its own set of occasional niggles and annoyances as well. The way the UI handles it can be misleading, and there are still the occasional errors where ending one character's turn ends all shared character's turns when it shouldn't.
I'd be very strongly in favour of a "shared Initiative On/Off" toggle in settings - I'd probably still leave it turned on most of the time, personally, but I'd like the option.
