I think you maybe misunderstood. It is not that you cannot push it out, but that you should not be straining in order to empty your pouch. Some minor bearing down is necessary in order to trigger relaxation of the internal sphincters. Only the external sphincters are under voluntary control.
You are not supposed to strain because you can damage your pouch that way (prolapse). If you need to strain a great deal, then you have problems. Either a stricture, twisting of the pouch, or pelvic floor dysfunction.
If you've been fine all this time, then you have not been really straining (or are just lucky!).
Jan