You can literally play BG3 as a third person turn based action game, with an over the shoulder camera. It’s entirely 3D.
Turn based and action are mutually exclusive. It is not and does not resemble an action game.
The assets are 3D. You do not play in 3D. You do not cast a spell and have the physics of your interaction calculated in real time while 10 other characters are simultaneously acting and having their spells calculated based on the real time movements of all the other characters. You do not hit a jump button and have where you land determined by your speed and direction. The actual gameplay mechanics are all pure dice roll. There are no 3D physics in play.
The absolute bare minimum:
Your jump must be decided by the vector of your movement when you hit the button. If it is not, there is literally nothing you can do to qualify.
Your actions must be aimed in real time and the outcome determined by the vector of your aim. Hitscan is shit, but it can qualify. If the action (not the vector of the shot) is decided by a dice roll, you unconditionally do not qualify.
There’s plenty more. But BG3 is not and does not in any way mechanically resemble a 3D action RPG. It has no common traits. The camera perspective outside of combat isn’t relevant.