The runner has to be more than three feet away from the base path to be called out. Allen only missed the plate by a few inches so clearly he was within the rules.
There are three types of players who play catcher: Hitters who can catch, catchers who can't hit, and the rarest breed--catchers who can hit. It's becoming apparent that Garver is in the first category.
Just had a chance to comment on the double steal. I'm surprised nobody here mentioned how Garver gave up on the play and didn't see that Allen's slide took him past the plate. Garver could and should have tagged him before he came back to touch.