Eh maybe we are reading too much into this as a cult. It seems at least half of us either chose to or can't visit other people right now. Let's say your town, if you got infected, you'd obviously not visit people. If you're on the scum team, you'd do the NK (not pass an infection) and your partner could do their night action. And apparently we have one guy who is just immune to it.
It seems like a really difficult job to spread a cult like that.
My guess is the knife is a TP NK with a % chance to actually do.
Just imagine the chaos if scum, TP, and town (through a FRAYDO mentor thing) all had NK's that were 100% chance (barring blocking). We'd be done by D3.