You folks are missing the point (said politely). If there's an incident where a player enters the protocol, the player cannot attest they are fine and have that considered with any weight. That's why they have the protocol. It's analogous to my workplace, and hopefully your workplace / any workplace. If I have an incident, in particular one where I collapse, and especially one with apparent cause, and it's noticed by my colleagues, there is an obligation to remove me from work for evaluation by plant nurse / first responders, (and most likely transported off site for professional evaluation, but in the Tua instance those professionals are on site at the stadium). I cannot assert I am fine and return to work. One can argue it's an employer liability thing just as much as it is a benevolent desire for the medical health of the employee - which is fine to argue - but it doesn't change the substance nor the validity of the protocol.
And as for lawsuit, your take is likely incorrect. If Tua claimed (Sunday) he was okay, that does not remove the obligation from the other party (team, doctors, 3rd party spotters and doctors) to prevent him from doing more damage to himself. To my point in paragraph above, the same is true. Even if my colleagues believe me, the standard they are required to hold is to err on side of caution and not allow me to return to my job that shift.
"Not enough time for proper evaluation" & "heat of the moment" doesn't fly either. You either take the time for a proper evaluation, or you don't let him play until a proper evaluation is done. Once entering the protocol, the error must always be Alpha risk (refusing to let a healthy player play) vs. Beta risk (unknowingly letting an injured player play).
Same with claiming "back injury". If he entered the concussion protocol, even if he claims it was his back - and even if it WAS his back - the stance must be to definitively rule out his head. There is a logical difference / nuance.
exactly
As with most outrage over "bad things that happen" in life, the issue is rarely to pass more stringent protocols / laws and rather to properly enforce the ones that exist. (Mine is a philosophical position on all facets of life. I'm not supporting the NFL, Dolphins, etc. I'm fine with more stringent protocols / laws, but only if it is irrefutably clear the existing were correctly enforced, which we will likely either never know in the Tua case, or we won't know the truth.)