FWIW, one of the tests the Army ran on the 1911 before it became the 1911 was to be sure the forward movement of the slide would let the extractor ride over the rim of a chambered round. The reason was thay they had the idea that magazines might become lost in combat and felt that the pistol should at least work as a single shot in an emergency. (The same reason they rejected a magazine safety.)
There is no problem when the extractors are made from the proper spring steel. Only recently, when most extractors are made from cheap cast junk metal (old chewing gum wrappers, I think) has there been a problem with extractors breaking.