Don't know the play you're talking about but if the batter swings and hits the catcher's mitt it's a catcher's balk and the batter is awarded first base and all runners advance if forced.
That's catcher's interference, not a balk. Batter doesn't get 1B on a balk. Also, on interference, offense has the choice of putting batter on 1B or taking the result of the play that happens after CI. E.g., batter could still hit a fly ball to CF & runner on 3B tags up & scores & O takes the play with the out.
Another form of catcher's balk is the catcher not being in his box behind the plate at the time of the pitch. I called that once as I was totally exposed to the pitch. Catcher wanted to have a clean throw to 2nd to catch a stealing runner so set up towards 1B with just his glove behind the plate.