My mistake. Threeighteen responded to a post by ooof about secondary barriers with a comment about IRCDs in cargo aircraft. So I got confused about which exactly they were referring to.

As for CASS, that doesn’t allow pilots to bring horse tranquilizer needles on board. The rules for allowing supernumeraries (background checks, employment by airline, random drug testing, what they are allowed to bring on board, etc) are vastly different than for pilots, mechanics, dispatchers, controllers, FAA, even flight attendants.

It’s a relatively small price for a reasonable added layer of security.