Firstly, I am far from a doctor.
This protocol in regards to cyclists with concussion, and just in regards to their safety in general, can be comparable a little to how we deal with covid, as in, that there is no right or wrong answer. Covid is about quantity of life vs. quality of life; well, that is how I see it mostly.
So with the concussion thing, what happens if a rider is in yellow, ahead by a few minutes, and in week three crashes hard on an alpine descent? He stands up, stumbles a little, but is able to get back on his bike. It is the final decisive stage in the general classification, and it seems as if he will be able to - if allowed to continue - finish the stage, retaining enough of his lead to secure Tour victory. But it looks like he very well 'could' be concussed, and the doctor is on hand to access.
The doctor makes a quick determination that he is 90% sure that he has concussion, and the rider is removed from the race. Later on, after more extensive tests, it is determined that no concussion is suffered. Everyone is left with one of the biggest what ifs ever.
So it is difficult to say if you should have a strict rule in this situation for all circumstances.
Yes, the safety of the cyclists life is important, but let's face it, if it was ALL important, then we wouldn't let these guys do the crazy things that they do on a bike in the first place. And so, the cyclists life is important, as is the quality of that life off the bike. But a MAJOR aspect of his (or her, in other cases) life is racing, and winning, especially if that race happened to be the overall victory of the Tour De France.
Because cycling is not like football, or basketball etc, I don't see how there is a right answer here.