I don't think it's that he's not Zinchenko, I think it's more a stylistic issue. Tierney is great as a more conventional full back that the large majority of teams still play, but he's not amazing at the inverted role.
I know there's a school of thought that says it's good to have alternative styles, but I've never bought into that personally. It's far more beneficial to be able to play the same way even when 3 or 4 players leave the line-up.
It's one of those where you might as well cash in because it doesn't suit anyone to persist.