I don't know about Quantum::Superpositions, but if it tries to implement current Perl 6 semantics, your expression should yield true as you thought.

any(2) is just the same as 2, so any(2) * all(5, 6) evaluates to all(10, 12), and all(10, 12) < 18 autothreads to all(10 < 18, 12 < 18), which in turn evaluates to all(Bool::True, Bool::True).

In boolean context that collapses to Bool::True, or in Perl 5 presumable 1.

So I suspect that QS is either out of date or has a bug.