I'd actually argue Trippier has played an impact. Three or four times he's played a ball in behind for Sterling or Mount. It actually does appear to be the main reason he's playing.Neither of the fullbacks has had much of an impact so far.
I could understand him playing if it's specifically to use that tactic, but there have also been one or two frustrating instances where Tripper has had the opportunity to burst past his man onto a through ball precisely the way Shaw has multiple times this season, and instead of going for the byline has cut back onto his right.
Not sure gaining the former is worth losing the latter.