Actually, I agree. I cite the 7 positions as evidence of why the Sox have kept him, despite the fact that his a jack of all trades and master of none. Right now, for example, Farrell is going with 13 pitchers, including 8 relievers--sadly, with some justification. That leaves 3 guys on the bench, one of whom is a catcher and normally not usable as a pinch hitter, etc. The Sox are officially carrying just 4 infielders--Devers, Nunez, Bogaerts, and Moreland. Holt is the only backup for 2b, SS, and 3b.
Last night the three benchers were Vazquez, Moreland, and Holt (largely, as you say, because of his abysmal OPS). Of those three, Holt was also the best choice to pinch run, which he did after Leon got to first on a wild pitch third strike.
FWIW, I'm beginning to think that last night's caught stealing was partly the result of a missed hit and run sign (or Holt read hit and run and it wasn't on). I say this because it was a 2-0 count, which definitely favors the hitter. Plus Betances, even with that 3-0 count to JBJ, was throwing strikes--9 of 14 for the game.
Interestingly, on a 2-0 count with Betances more than capable of throwing a strike, that third pitch was outside, perfect to set Sanchez up for an accurate throw to 2b.