Cracked block cause?

That is very interesting, and I would venture a guess that the only force strong enough to crack a (stock unmodified) block in that direction would be freezing. I don’t even think you could split one like that with the wrong cam bearing tool or being overly aggressive with one. Regardless, it sucks and it’s junk.
Only problem is, there's nothing "to" freeze there. If it was submerged in coolant on those areas, then yeah, but it's not.