I didn't intend "perfectly confident" to imply people literally assigning a probability of 1. It is enough for them to assign a high enough probability that it rounds closer to 1:1 than 1.01:1.

That isn't enough. Neither the actual behaviour of rational agents nor those following the instructions Carl gave for the survey (quoted below) would ever choose the bad deal due to rounding error. If people went about one boxing at 0.999:1 I hope you would agree that there is a problem.

What is the lowest payoff ratio below at which you would one-box on Newcomb's problem, given your current subjective beliefs? [Or answer "none" if you would never one-box.]