Breaking the glass is true, but you'd have to find a pretty big, adult Odontodactylus scyllarus (Peacock Mantis) to do it. I've only heard 2 or 3 actual happenings of this, but it is quite possible.
When it does happen, it is mainly caused by one thing....not having a deep enough sand bed, for them to burrow. They'll dig through the sand, reach the bottom of the tank and give it a whack, to keep burrowing, and will break the glass.
I've kept a few, over the years, and have had them strike glass...but never broken it.
And yes, the velocity of which they strike their prey is the same as a .22 bullet, from a pistol.