I think there is a misunderstanding as what counts as an observation. I think your point of view is something like "Yesterday I experienced a universe consistent with the laws of physics, and the day before that I experienced a universe consistent with the laws of physics and so on. I'm about 30 years old so that's 10,950 observations" to which I ask "If you have all that knowledge, what did you have for dinner 78 days ago? Was it consistent with the laws of physics?" to make the rhetorical point that a boltsman brain does not need to fake any history, it only needs to fake your current memories of history, a much easier task. Boltzman brains are very similar to Last Thursdayism.
In the Alice and Bob example aren't the rules of the game part of the natural latent? Like Carol also needs to remember that neither Alice nor Bob will draw any [color that isn't purple] lines and this information isn't in the green lines.