Then there’s the issue of narrative intent. At no point during the War Arc was Kakashi’s reaction speed ever treated as something extraordinary. I can understand that argument being made for Minato to some extent, but definitely not for Kakashi. No character looked at him and thought his reactions were on such a godlike level that top tiers like BSM Naruto, Juubito, Rinne Rebirth Madara, or even one-eyed Madara couldn’t touch him due to some massive speed gap.
For god’s sake, by some of these interpretations, Kakashi’s final reaction speed would be 500 times faster than Juubito’s movement speed, which just doesn’t track with how the story actually portrays him.
Even more so, the feat in question was performed by an exhausted Kakashi with no mental amp involved.
With how insignificant the feat itself is, I'd just rule it as an outlier