Oh, sorry, my bad.
In that case, I suppose it's possible that the author actually believes this, but it may also be possible that the author is simply setting Akane up for a reality-shattering revelation about the subject later on down the line.
In fairness to Akane, she's what, 16? Not remotely surprising she'd have an unhealthy view of some aspect of show business, particularly in a series where the entire premise is "show business sucks and everyone involved badly needs therapy".
At this point I'm taking the credits pages as less reaction to the developments in the story and more "here's what happens to the human body when it drinks a liter of milk in under half an hour."
Given it's established that she lied about the cheating thing, it seems reasonable to assume that her motivations at that time are going to be an important plot point further on down the line. Gotta get world-building and relationship-building in to make sure we're emotionally invested in...
To me, it's not entirely unexpected that she's got some athletic prowess to her, given she was the one that threw down the original challenge. Granted, her assumption was that Epetarou was a stereotypical nerd, but it's clear she believes in herself to at least some degree.