This is impossible to implement in practice though. Scrollbar "blocking" as you call it, is just an overflow: hidden CSS style, which is perfectly warranted and needed in some cases on some elements.
How do you identify which element is the "main" one for the given website? It doesn't have to always be <body>, it could be something which is nested.
How do you identify which element is the "main" one for the given website? It doesn't have to always be <body>, it could be something which is nested.