wtokyo I'm not convinced you're very experienced working on bikes if you've never seen this happen. I am confused on how you don't understand how extraction threads could be stripped. It seems pretty straightforward? Puller in, torque out, threads yanked. Not too confusing.

This set of cranks was brand new on a brand new SG75 bb. The crank puller is my trusty park ccp-2. Naturally, none of you have met me or know who I am, so you'll be the first to claim user negligence. There was no grit inside the crank preventing the puller from seating all the way, nor a hiding washer. The tapers were greased before I installed the arm, and I even lightly greased the puller threads. Bottom line is the crank arm was seated on the spindle with more torque than the aluminum extraction threads could handle, and the steel puller bit them off on the way up.

I'll be the first to admit when I'm wrong, but this was one of those rare occurrences that cost me money, and not necessarily any new knowledge on the R&R of square taper cranks.