Dang...

But it seems unlikely (to me) that the motor could fill the entire bore with water when running at 7K rpm. I'm no expert (even if I have stayed at a Holiday Inn), but just seems like too much volume to fill up and hydro lock the motor unless it was sitting still.

You wouldn’t need to fill the whole bore. For example, zero deck piston with 5cc for valve relief, 7cc for head gasket, and 65cc for chamber, you can hydro lock with as little as 77cc of water.