Aye, there are definitely cases where the answer isn't nonsense.

Even for sets though, "a in b < c" isn't an intuitive spelling of "a in b and b < c" the way that "a < b < c" is an intuitive spelling of an ordering relation.

Hence filing this as a low priority issue - it's a weird quirk, and potentially worth changing to avoid a particular "Wat?" moment when folks first see it, but it isn't a bug magnet the way some other historical constructs have been.