Wouldn't this apply to ALL firearms that have a "snap over" extractor?
In fact yes. In time all push feed extractors wear, or fatigue fracture. I have helped replace a push feed M70 extractor on the firing line. The match director happened to have Win extractors in his truck, and we all sat in a circle and removed the shooter's extractor, and fit a new one. With the M70 push feed, it slides out of the way. So what happens is wear, typically on the sharp end, and cases fall off the bolt face instead of clearing the receiver opening.
The Rem 700 extractors wear out all the time. Might as well stock up on replacements before factory extractors go out of production.
Claw extractors will fatigue fracture, especially if required to snap over a cartridge rim. This is very hard on an extractor. I had one break on a M1903, happened in rapid fire prone. Cartridge jumped in front of the extractor and instead of bending over the rim, the extractor broke. The M1903 extractor was designed with enough bevel to snap over a cartridge rim, but that extractor was old, and it broke. I recommend for all rifles with a claw extractor, to feed from the magazine. Do not require the extractor to bend across the cartridge rim. Back in the day, when pre 64 M70 extractors were out of production, it was difficult if not impossible to find a replacement. What some did, was to modify M1917 extractors, (with enough grinding) to fit a pre 64 bolt.
Anyway, I am leery of extractors, such as the push feed M77 extractors, as I know it will break, and then, where do you get a replacement?