Never happened to mine. Some have told me that if you constantly use the slide stop lever to let the slide come forward instead of pulling back on the slide and letting it go, you can "round off" the metal and this can happen. But it would have to be a very high round count gun, I'd think.
No offense to your friend, but I'm gonna call BS on that one. I had a new slide stop in my CZ-75 due to the old one being really old and breaking (old pre-B, slide stop is a wear piece).
A couple jobs ago, the firearms instruction I received stated that the glock manufacturer specifically states that you should never use the slide lock (or "slide release") to release the slide...ever. They said it was designed only for locking the slide back, and constant use (using it to replace a fresh mag during reload) would wear down the lever.
They made us pull the slide back and release it to load it.
If they didn't mean for it to be used they probably wouldn't have wasted the time an money to put the grooves in it. For that matter you would think they would have made it completely internal requiring the user to pull the slide back to release.