I agree just "stopping" the character would be ideal, but since you already gave an input to go somewhere, I believe the easier thing for Larian to do is the auto-turn base since this mechanism already exists (when hostiles spot you for example) and I imagine it wouldn't need as much development time compared to introducing a new mechanism that just stops the characters from moving while still being in real time.
But this behaviour, too, already exists. When you click right mouse button while your party is moving, they will stop moving.
