My purely speculative guess would be that this is less of an issue for tankers than for fighters.
Fighters are designed to be able to take off with both weapons and fuel that they are supposed to use up before landing again.
Big passenger/transport jets may have to dump fuel to be able to get to their landing weight, but they normally don’t drop their cargo or passengers during the flight. So for all of the “cargo weight” that is taken up by fuel in the KC-135, it should be possible to bring that back without dumping it.
But maybe @ST0RM can say something about this if he’s allowed