Is this really the case?

In fuzzy logic, one requires that the real-numbered truth value of a sentence is a function of its constituents. This allows the "solve it" reply.

If we swap that for probability theory, we don't have that anymore... instead, we've got the constraints imposed by probability theory. The real-numbered value of "A & B" is no longer a definite function F(val(A), val(B)).

Maybe this is only a trivial complication... but, I am not sure yet.