It probably did not take any extra development time. They were going to give us the ability to respec our player characters and hirelings. If anything, excluding companions from this system would have taken slightly more development time (by a few minutes of coding) than just making the system universal to all characters.
Except that they had to implement and test a system to separate a characters in game class and cutscene class and had to ensure that there is no point in the game that would break when a origin character suddenly did not have its expected class anymore.
For that effort they could likely had added stat rolling as rolling dice is also already in the game.
What’s a cutscene class? If Gale casts a spell in a cutscene it’s all pre-rendered. It has nothing to do with his class at all from a mechanical standpoint.
Larian probably did spend some time testing to decide if they want the game to react to a character’s change in class, sure. But the QA team constantly tested systems for lots of things that were or weren’t implemented in the game. You can’t point to any one of those and say “this is why I don’t have the feature I want.”
For the purpose of reactivity the origin characters will still count as having their original class and not the respecced one. So instead of reactivity checking the class a character has they now have a class for cutscenes and a class for gameplay.
Also its not only cutscenes but also quest design. Now you cant have for example a personal quest for Halsin that requires him to use wildshape to get past obstacles because the archdruid might not be a druid anymore.
