I'd like to repeat the point that BG3 is a party based RPG.
Players being able to freely run around in another area while someone else is in combat shouldn't even be a consideration. This is not an MMO. You are supposed to act as a group of 4. If the party needs to split up momentarily the slow down is acceptable. And it keeps the party in sync.
So +1 to pausing the entire world at a time and preventing exploits and all kinds of nonsense.