Combine orderBy_ with join_

If I have a `join_` where I compare some row's value to the `primaryKey` of some previous result in the same query, I can no longer `orderBy_` directly on that `join_` (due to a mismatch between `QBaseScope` and `QNested QBaseScope`). Instead I have to move the `orderBy_` to the whole `select`. Is there a reason the result of the subquery returning the foreign key can't be more polymorphic?