Just to nitpick, in the section after "On the other side, these following guards are more of a “you really shouldn’t do this” variety – much closer to a disabled state in graphical user interfaces:"

The second and third examples are safety lockouts [0] working as intended: Some system is locked in the off state to ensure safe access for technicians.

Especially the padlock lockout is simple and effective: As long as you have the key in your pocket, you can be sure than no one is going to turn on the meat grinder you are cleaning.

[0]: https://en.wikipedia.org/wiki/Lockout%E2%80%93tagout

Isn't the third one just a sticker?