Didn't someone say the guy that built the 318 stroker motor had run it for a couple of years? Not like he built it and blew it up on the first run.
Not saying anyone is wrong about the assessment on splitting a bore, seems like a good possibility based on how much it was bored. 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. And the crack is at the bottom so it wouldn't start taking in water until it was at the bottom of the stroke. Just saying the fact that the piston was sideways at the bottom of the bore suggests to me that the crank broke first, turned the piston sideways and split the block at that point. Add that it was an Eagle crank and (per above comments) not the first to break this way.
Not saying I know what I am talking about, certainly much more experienced individuals here than I am. Just an observation and thought.
Back to the idea that he ran this motor for a couple of years, seems like he is due some credit for making it work that long even if it did fail spectacularly. Even if we don't agree with his method.