He Does, Especially Since He'd Built it Originally to Protect Himself
When Stan and Fidds were first turned, Fidds was under the impression that Stan would be a mindless brute who would try to kill him in his sleep, so he built the collar and made it in a way that only he can take it off.
Truthfully, Fidds had planned to sneak it onto Stan's neck when Stan was asleep, but he eventually got to know Stan as a person, fell in love, and tossed the collar in a locked safe.
The only reason Stan's wearing this specific collar is because Gideon had a few lackeys (Read: Fae) check the shack and discover it. Bud then threatened to not only convince the town to kill Stan, but to tell Stan who created it and why.
Stan has no idea that Fidds made the collar, he's more under the impression that some sadistic human made it and gave it to Fidds, who would do anything to keep Stan safe, even if it hurt him.
The first time Fidds saw Stan get practically electrocuted, he threw up and begged every higher power listening that Stan wouldn't find out.
