Nobody expects the scroll behavior to be different on a webpage, so it's always a surprise when a page does something like this. Then, you have to learn to adapt to how it expects you to scroll so that you don't screw up its animations or overshoot.

It's the kind of UI that works if you scroll a specific way. A lot of people probably do. But if you don't, it's all very tedious. I consider that to be poor design.