This seems to only be a animation error?
I'm not completely sure what an "animation error" refers to in the osu! code, but if this was only a visual issue, then why would the game not recognize those big notes correctly? Even though the max amount of points can still be obtained with this issue, the game does not think that a big note has been hit correctly. Even the scores on the online scoreboards say that no big notes had been hit when the max score had been given. Most of this problem is probably related to simple animation, but there also appears to be some element of a recognition issue as well. Although, I don't know the details of how the osu! program works, so I may just be misunderstanding your point.
Thanks for coming back to this thread either way!