[brownbat]

Another way to conceptualize the "cropping" is to get rid of all future states where planning would have been meaningless anyway.

We are momentary Boltzmann brains? We'll assume not, because if so, nothing really matters.

Trivial difference, but that avoids potentially difficult threshold problems and cousins of the St. Petersburg paradox or even Pascal's mugger, at the risk of being slightly more hand wavy.

Arguably an aesthetic distinction at this point, I generally think your description and approach are right.