I take you dont take apart engines. You dont measure pistons, cylinders, crankshafts, etc.
We ride in the mountains. Ive blown an engine miles from the trail in 5 feet of bottomless powder. It took 1.5 days of disassembling that sled so that 3 of us were able to pack it out.
Everything on the sleds get inspected before every trip. And engines get torn down every 2000 miles. And while some pistons are usable, they all have enough slop to warrant replacement. And yes, most times I notice a performance increase. Tighter fit, better compression, better horsepower.