detonation huh?
where are the signs on the top of the piston that would indicate detonation. that looks more like dame i saw on a piston that was not installed correctly (yes I have seen ring lands break off like that from inproper install). the scoring is from the broken parts going up and down, cyl head looks good ok also.
if that motor detonated that hard to break the side of a piston I would suspect some other damage to top surface or some melting or something.
thye are just covering there ~~~ so they dont have to re-doo your motor.
I say build it up yourself. the best quality control is yourself...
sorry to hear that the motor went south you you.