Here is another perspective to consider that may or may not be helpful to the discussion about this issue. I have never ever played any kind of turn based computer game in any genre in which I felt immersed in the game. To me every turn based computer game I've ever played felt like some variation of a tactical or strategic wargame and not much different than playing chess or checkers or cards or Risk. I have never felt any sense of urgency when playing a turn based game. It never feels like when I make a decision matters in the least. But all of the RTwP D&D games I have played felt immersive to varying degrees, especially during a challenging combat encounter when my party was outnumbered or outgunned by a higher level boss. RTwP D&D games feel I'm a fireteam leader or squad leader trying to lead my fireteam or squad while I find the balance between managing them enough instead of micromanaging them too much.
So, at least for me, if BG3 is turn based it will not feel like an immersive RPG. It will instead feel like an isometric fireteam level tactical wargame with RPG elements. It will not feel like any D&D game I've ever played before. It won't feel like D&D or AD&D. It will feel more like isometric Squad Leader with great graphics and role playing elements for icing on the cake.
That's fine. I feel almost the exact opposite. All the pausing in STwP destroys anything like "immersion" (I think I hate that word). TB feels much more strategic (yes, kind of like chess). And conversely, every last action matters, however minute. Lastly, TB feel much more like D&D, because that's what D&D does.