As long Narvaez can play, and Wong available. you are correct that Sanchez adds nothing, given his NO bat.
If Narvaez reinjured ir aggravated the knee in a game , Wong takes over and they can call Sanchez up over night.
It may have to do with # of options left to move Ali S OR no pressure on the 40 slots right now. so leave him up. The 26 roster is more critical to manage and Sanchez is costing them flexibility