Ataxia is definitely a symptom of a concussion. How can someone claim no concussion symptoms were found when impaired balance and coordination is definitely a symptom of a concussion.
And oh, BTW, you don't have to take a hit to the head to get a concussion, a severe shaking/movement of the head can cause it too. So just because a head doesn't touch the ground super hard, doesn't mean it rules out concussion.
If the new rules are such that if there's enough symptoms and evidence that if the diagnosis might be off, it's best that the player needs to sit the rest of the game, so be it.
I don't see that under new protocols that the NFL did anything wrong. Teams can overcome losing a QB for most of one game and still win titles. (Pats' won a title with Brady missing 4 games.) Better to err on the side of caution and not risk players with the highest pay and drawing power getting severely injured by having a Tua situation happen, if Tua was actually concussed during that Sunday game.