If you steal home and the pitch was a normal pitch, this locks up the catcher for a decent amount of time and they just stand there. If the runner on 3rd is fast enough, they will easily score before the catcher gets "unstuck". I'm sure this is SDS trying to implement real baseball rules as with a normal pitch, the catcher has to stay in the catcher's box until they have the ball. WIth a pitchout or a throw home from the pitcher (where the pitcher steps off to throw home to catch someone stealing) the catcher can move out of the box for the play.
It is a good idea in theory but in practice your catcher has the ball and just stands straight up and can't be moved for a little bit and your Robinson's and Turner's can easily run past them to score.