If it's DnD and the campaign takes place in or around Balder's Gate, and it's called BG3, then it's BG3. Everything else is totally trivial to the game being BG3 or not. There's really nothing else to be said about it.
Like I told you on the steam forums,then Baldur's Gate:Dark Alliance 1 should have been BG3 but it's not for a reason,it's a diferent game with a diferent story with a diferent genre as any other game taking place ''in or around'' Baldur's Gate so I don't agree in the slightest.