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.
Truth. The Bhaalspawn saga has ended anyway; so there isn't even a story connection. It is simply a new grand crpg featuring BG.
