(Too late to edit, so replying to myself instead.) I'm going to backpedal a bit on my point about manual scrolling being the same thing as automatically scroll

(Too late to edit, so replying to myself instead.) I'm going to backpedal a bit on my point about manual scrolling being the same thing as automatically scrolling directly there via anchor. The scrollbar can be at various positions, and if an anchor takes you there automatically, it jumps to position N, never passing through 0 .. N-1. Whereas if you manually scroll, you pass through all of 0 .. N. So whatever resources are above the target position would not necessarily be loaded with an anchor but probably would with manually scrolling. So the externally observable wire behavior (DNS, IP addresses you connect to, etc.) may still be different. So if you manually scroll, the adversary can infer that there's something significant about scrollbar position N. It might just be that there's where you lost interest, or it could be that that's what you found interesting, but it's not giving away as direct a clue as jumping straight to position N.