He gets it wrong a bit as the margin for error works both ways, so the stumps are the same size on balance. I do think the margin is greater with spin than seam, particularly if contact with pad is very close to it pitching.
The key has always been to appeal, you get two plumb turned down, they give the third even of it is more doubtful.
but its the umpire that controls the margin and not technology ? what i don't like is the umpire controlling the amount of reviews you have left in not giving it not out or out knowing you have a review. so if you only got one left and the umpire is clever he can make you use it
i would still like the team coaches to have a couple of reviews as well. because you can upset a umpire or he does not like you and he will give you nothing. just like the tour in india they used home officials and they got the advantage as well as DRS