I don't think it's true about all the companions... Shadowheart's character development actually requires you to have her in your party during your travels and most of the revelations concerning her are a direct result of going to specific places on the map with her... Astarion is probably the one who's interactions in the camp are the most significant, but you have some interactions in the world map with him as well.


Larian's Biggest Oversight, what to do about it, and My personal review of BG3 EA
"74.85% of you stood with the Tieflings, and 25.15% of you sided with Minthara. Good outweighs evil, it seems."