They are definitely Steyr bolts, multiple late rifles have shown up with unumbered e623 bolts, like Mike is mentioning. Quite often armorer parts show up on Bnz45’s and all from other makers, naturally the then defunct makers of 98k’s shed their parts to the industry, so e37, e26, e214 Etc show up. One of the most common parts, being extractors, and rarely, sight bases will show up. Of course to authenticate these parts as having actually been assembled by Steyr requires looking at the balance of the rifle and many small telltale features that would indicate an original assembly or a later addition. Quite often these type of parts are opportunistically used to “correct” something. Not having seen the rifle you mentioned Georg it sounds suspect at first, but oddities do exist, so it’s worth a look.