You have a flawed reasoning. You assume after a successful exit it will be the end of everything and there will be peace. On an unsuccessful exit however you wake up with brain damage thinking: oh noes I fd up.
Why do you take the first one for granted ? If science holds any ground in this universe, the same science you apply for your nitrogen exit, then all fear of brain damage is completely pointless.
And to be precise, you won't wake up. Your body will. You, your personality, yourself will be erased after 5 minutes without oxygen.
What happens after a successful exit is something that maybe not belong in this thread, but more in a thread about existential questions.
And no I don't assume that a failure after passing out is a certainty for brain damage, I see it as a risk (something that scare me)
If the flow of gas isn't enough to flush co2 in correlation to the consumption of gas and expelled co2, so it results in a build up of inert gas and co2 to a level where it's not possible to freely breathe the gas. Let's say this happens after being passed out, and someone wake up from an hypercapnic response, I fully respect if you believe that it can't result in brain damage. I do believe it can though.
Tbh, sometimes this forum can be annoying, if someone question risks about something, important questions that need to be discussed, then some people tend to "protect their method" and like "Say anything negative about this and it's fear mongering"
Btw do you have any measurements of co2 levels at different flow rates like 15-20-40lpm when breathing over minutes (with breathing oxygen and not inert gas of course) that would have more value, than what you just think, or rather what you feel so certain about.