The tune was not your problem.
Your ring end gaps were not correct for the amount of boost (increased cylinder pressure). This caused the rings to sieze in the piston ring land & break the top of the piston. I've seen this many times when someone builds a motor & swears they'll never use nitrous (increased cylinder pressure) & then they do. I've seen it with cheap pistons & good ones.
Yes and no regardless of tune you have mechanical limitations of an engine. I don't know how much boost they were running so we don't know if they were expecting to much from a stock engine But, an improper tune can cause the same damage. The best description I have read has come from tune it 2 pdf from mr mopar. So if this damaged occurred at reasonable boost levels lets say <8psi I would blame the tune especially if running a diablo tune. I personally ran one for over 8000 miles and was not happy with it. The factory lx pcms don't work well with boost. I personally drove several forced induction set ups from different vendors and different tuners they all seem to have the same fuel control problems. That is why I am trying a different engine management route & hope it prevents this problem .
"Top Ring End Gap is often a major player when it comes to piston problems. Most
top land damage on race pistons appears to lift the land into the combustion
chamber. The reason is that the top ring ends butt and lock the piston at TDC. Crank
rotation pulls the piston down the cylinder while leaving at least part of the ring and
top land at TDC. Actual running end gap will vary depending on the engine heat
load. Piston alloy,
fuel mixture, spark advance, compression, cooling system
capacity, duty cycle, and Hp per c.i. all combine to determine an engine's heat load.
Most new generation pistons incorporate the top compression ring high on the
piston. The high ring location cools the piston top more effectively, reduces detonation, smog, and increases Hp. If detonation or other excess heat situations
develop, a top ring end gap set toward the tight side will quickly butt, with piston and
cylinder damage to follow immediately"