If he had turned the wrong way, he wouldn't have been able to make the initial catch, his depth on the route would be different, which changes the timing, and the pass would have been 3 yards to the side.

There is no way he turned the wrong way on that route on a timing pattern like that, the ball is released before he even plants to start the comeback.

I am not saying I don't disagree that it should have been a sideline out dig, but that clearly wasn't what was called.

Your issue on where the route should have been is a play calling issue, not a Tanner WR technique issue.