I have only heard of one single case, ever, in WW2 where a tank was destroyed by dropping a grenade inside. It was a German soldier who saw russian soldiers banging on the hatch of a T-34, the commander would open it, speak to them, then button back up. He snuck up, climbed up, banged on it, shot the commander, and dropped in the grenade.
Obviously, one account does not a rule make. If the russian commander had kept buttoned up, there is simply no actual way that anyone could open the hatch. This is not saving private ryan. Tank hatchs LOCK on the inside. Sorry, but movies are not historical fact.