I'm not sure whether my guesswork was helpful, but I think the whole "probabilities" thing is not helpful here.

The teacups-floating-around-Saturn example was loosely copied from Bertrand Russell.

What my guesswork was aiming at was that my only meaningful interpretation of the example, taken as a riddle, with "free variables", was that the conclusion is wrong as in "not derivable from the given facts".

I agree in that I'd prefer to encode this as "I don't know".

But depending on how you interpret "false" and "true", the conclusion is false, and stating something as true that cannot be proven is false.

It's not very intuitive until applied to abstract terms instead of concrete ones, and I'm sure there's a fancy name for this higher-level logic.