I think it's more like Larian supporting gameplay, and knows that an option like this can improve replayability.
Can you elaborate on how it improves replayability in your view? If I can try any class and any party composition at any time I want in a single playthrough, that's one less reason to replay the game.
I don't really get the "try any class and any party composition in a single playthrough" thing. If you respec a character at level 10, you haven't played that character from level 1 to 10, you haven't played that party composition and classes during the playthrough. I mean, unless you save and reset before every fight and every section respeccing everyone to try every possible different permutationts, but doing so your run would last easily 10.000 hours.
The way I would use this is playing the game once, maybe twice, as it is, THEN making weird runs where I change companions into something else. I would change them from the get go and bring them all the way through, with those classes facing the whole game in a different way. I would be able to do the same thing with faceless hirelings, obviously, but I find that hirelings are kinda boring so I rather respec the companions.
I think I see what you mean. The question is, do I need to replay the whole game for another 100+ hours to truly experience a class? Given how much reactivity BG3's gonna have, the answer may as well be yes. In other games I'd be inclined to think if I play a barbarian until late game and then switch to bard, I've pretty much experienced the peak of what it feels like to play a bard and there's no reason to spend another 100 hours in the game just to try a new class. That could arguably be a good thing, it sure saves time, but in context of replayability it would take away a major reason to start over.
It can definitely spice up companions on subsequent playthroughs, though I think that could already be done through subclass selection, feats, equipment, multiclassing and, most importantly, story decisions.
