After them being so intricate with him and his storyline, and his journey with Brienne, that just isn't....compelling enough of a reason for me. That it was "always bound to happen".
It also ignores the nuance of how they chose to present show Jamie as a person, his arc + journey, etc. it undermines the character as the man they showed us who was battling with issues like loyalty, honor and the like.
You make it sound as if he was a robot who was programmed to "return home" the moment his duty was fulfilled and that's not the case, again, cuz of what the show runners chose to do with him.
You don't have him have the bath scene with Brienne then fast forward to the keep burnin' and the outlook he had then if that was your OG plan.
If it was "he was always going to go back" and then that's just that, then it's cheap, manipulative and

on their behalf.