I can't say concerning other semi-autos (I think different ones have different mechanisms to provide this kind of safety ... and cheaper guns are less likely to have them) ... but, specific to 1911s, there's a "disconnector" link in the trigger-to-sear mechanism. It moves up-&-down into a small recess in the bottom of the slide. If the slide isn't ALL the way forward (i.e., with locking lugs "locked"), that recess isn't over the disconnector, the disconnector can't move up, and the trigger-to-sear mechanism won't release. So, if the slide is pushed back on the barrel a little (as described by the author), it won't fire. Similarly, in the more-recent 1911s, there's a firing-pin block that won't release unless the slide is in the right position. In any case, as I say, this a perhaps true ONLY of 1911s. Your gun may vary.