I don't mind designers overriding when they take meticulous care to craft a better tailored experience. But once I scrolled past the initial content I found the site a UI disaster. Not long after it said "Pick a person to explore", I wanted to tap a particular box to read one of their conversations, and couldn't figure out how to bring any dialog up. I wound up scrolling further down afterward to see if that was how to trigger some dialog for my selection, and all the boxes started moving around at seemingly random, performance tanked and the whole thing got stuttery. I couldn't scroll back to where I was or find that box again that I was interested in. I left in frustration. Design fail, as far as this user's encounter.

I feel the same. I don't particularly mind if a developer overrides the scrollbar, and I would actually argue that in this case it was a good way to present the story and overall I liked it, but you need to do it right. If the sites becomes all clunky, it stutters, and you get text popping up a while after you scrolled, then it's better to focus on the performance and leave aside the animations.