The part about the Stg-58 having select-fire you could just "remove" make me laugh. No select-fire weapon can be converted back and forth like that. Who calls .45 ACP 11.43 x 23mm? I've never heard that in my life. Otherwise, the article seemed somewhat tech-savvy, even with the firearms.
Incidentally, to shoot the Stg-58 in CA requires a 10-round magazine as well as a mechanism to lock the magazine release in place so it requires a tool to release it. Removing select-fire has nothing to do with CA legality, if you want a select-fire weapon you need a class III license and you need to be in a state that allows class III (NV, UT to name a couple).