Wouldn't this all be easy to prove or disprove using random walks? Just run a thousand or so, from different starting points, and see where they all go, picking

Wouldn't this all be easy to prove or disprove using random walks? Just run a thousand or so, from different starting points, and see where they all go, picking recommendations truly at random (without bias towards more extreme stuff). If Youtube truly pulls you towards extreme videos, then you would always end up at those videos after a long run.