In my mind, Pogo Sticking is a ranking signal. The reason being, it clearly shows what is and isn't satisfying the user's needs.
If Google's users are consistently clicking away from Page A, to Page B - it's clear that Page B is better than Page A for answering whatever the user's needs are.
To me, this shows crystal clear evidence about the quality of a page, and how well it matches the user's needs. I don't see why Google wouldn't use Pogo Sticking in its Algorithm.