I don’t think anyone thinks Elko will be some sort of savior. It’s just that Vaughn is terrible and Maton is the primary DH. Also, Elko isn’t getting any younger (27 in December) so it seems reasonable to see what he can do.
But to your point, since Quero will likely see time at DH, Vaughn is probably the guy who needs to go to make room for Elko.