I struggle to see what BP could have done that would have caused replacement pistons to break?
Sounds like OP has something else going on causing the pistons to fail in the first place. Detonation? Timing? I'd suspect the EFI might have even unintentionally leaned out at some point.
I've been beating on my BPE shortblock for 5 years now with tons of abuse. The only things that broke happened when I sent a hardened washer down the intake. Replacement piston and ring set from BPE still going strong.