Chained might be a way for the game to understand who is suposed to be there, but i think there are 2 things to consider:
1. I think Larian wants to maintain the option for every player to have custom relationships with the companions therefore no shared dialog in this case (keep in mind there is already a distinction between companions and regular NPCs so that shouldn't be a problem).
2. This mechanic is just for player created (and probably origin characters selected at creations) mechanic, so I think it could be possible to have companions in generel to join discussions (there is no issue with guidence either no matter who has it in the party).
Basically, I think the only place it might be an issue is the personal dialogs with the companions, as I think the other dialogs could be already using a different dialog-system. But its hard to say what systems are connected on code-side. I hope Larian gives us there some options.
