To add to my previous comment, I would've kinda got it if the stamina thing was already an established issue beforehand, but not only was Himeno previously shown to be capable of competing in back-to-back matches (and make the distance in one of them), but Shino-sensei even credited all the running/roadwork Himeno did during her 6 months away from the sport for helping her maintain her endurance for her comeback, so having endurance suddenly become her fatal flaw during her last match after previously establishing that endurance isn't a big issue for her, especially when she hadn't participated in any prior matches that round, just doesn't make sense in my eyes.