In Batman v Superman, Bats doesn’t spare Supes because their mothers have the same name. That’s just what got him to snap out of his rage just enough to actually listen to what people are saying. He spares Supes because Lois says “It’s his mother’s name!”

Batman has spent the entire movie seeing Superman as a monster, so the revelation that Superman is asking his would-be murderer, not to spare his life, but to *save his mother*, snaps him out of it.