You have a couple good points. Yes, jagex does have an automated system that can detect suspicious people, but tbh, I still believe that Jagex moderators have to be the ones to ban. They are simply given the list by the "detection bot" and then decide whether to ban or not. They may also look at the players history etc, if it is a main account, an account with high woodcutting just wcing yews, or w/e.
I wouldnt recommend doing the same skill for an extended amount of time, because that (in theory) triggers their detection system.