Yes, because sage isn't a new function it's one that was taken from 2chan and like the post says sage never was and never will be a downvote. It's just a way to reply without bumping the thread.
...which, based on how the boards work, is essentially a downvote.
Each thread can have x posts before new posts no longer bump it. If you sage, you are using up that thread's available space (1/x worth) without bumping. Although this doesn't "downvote" in the sense that the thread is penalized/lowered, it "downvotes" because it takes up thread space with no benefit to the thread. Not to mention, sageing is a way to express your dissatisfaction with the thread, which I think was always the point (rather than trying to actually hurt the thread).
