I disagree in this case. Normally I'd fully agree with you but I think this animation style works really well given their use-case.
I did find it useful to scroll up and down with care to understand their annotations in detail.
Same i normally get so much anger, but in this case it didn't slow down scrolling, also it added functionality instead of "just looking good".
I always thought scroll jacking was taking over the behavior of the scroll? This seems different, as it's using the position on the page to run the animation but not controlling the scrolling behavior.