The puppet saw your post and was disappointed

Okay but did Henry know? Did he ever find out? Did William attempt to use it on him too?

No one else was tested with the device at the time. Too dangerous. See, Fritz was a perfect lab rat because 1. He was the most aloof person Will knew and 2. If Fritz caught on in any way, no one would believe him. Henry is a respected authority figure who has established relationships with the community. Fritz isn’t.