It's not great design. It's a dirty hack that might work for some people, but is a non-standard practice that abuses JavaScript to achieve a certain effect. Overriding scrolling behavior might work if you're scrolling with a mouse or trackpad at a consistent speed, that that might even work for a majority of the site's visitors, but for others it breaks. If you press the PageDown key to get to the next page, it doesn't work. If you scroll half a page down using another key combination, it doesn't work. If you use a text-based browser, it doesn't work. I didn't test it using a screen reader or other types of browsers, but I can't imagine it would work that well there, either.