This is how i see normal bolts and stretch bolts. I'm sure i'll be corrected if i'm wrong

All bolts stretch when torqued up, however a stretch bolt is designed to stretch further than the elastic limit of a normal bolt. At this point a normal bolt will break.
The effect of this is once the bolt has stretched, it compresses against the thread, in effect making it like a 'self locking' bolt.
The reason these bolts must always be replaced is once stretched, they will be need to be torqued up even tighter to 'lock' the bolt. Therefore you cannot know if you are using the correct torque and risk breaking the bolt as it will be weaker.
Normal bolts will not stretch in this way, so are normally ok to re-use.
The other method of locking a bolt is loctite, which prevents the thread from vibrating loose.
Also nuts with nylock or slightly off shaped nuts can be used to lock a bolt/stud.
The bolts used on a golf rear caliper are small, but are only tightened to 26lb ft. At such a small torque it is very unlikely that distortion,stretch or damage would occur.