J. if they are over torqued they then they theoretically have gone past the yield point and its at that point that they begin to loose strength. The torque spec is meant to keep the bolt within its elastic range. The bolts can stretch just as a strip of metal can bend and return to its original state. It’s only when you go past the yield point that it stays stretched or bent.
I've got 66years on me and have been around engines ever since I was a tot, pop being a mechanic. The recommendation to replace the head bolts each time the head is re-installed isn't new it's been around ever since I can remember. I don’t think I ever spent the money on new head bolts and never had one go bad on me. I worked as a parts man all through my teens and don’t ever recall selling a set of head bolts.
Denny Graham
Sandwich, IL

Denny G
Sandwich, IL