I've done many runs in the chambers, and experienced Hypoxia in various scenarios.
Two things I learned. One is that I personally feel really good when hypoxic. Like, really really good. Yet the video showed I was pretty much stoned.
The second being that the effects of hypoxia during night flying weren't really noticed - until I put on the oxygen mask and noticed that the lights got brighter and stopped moving around (they were glued into the wall).
So for everyone without training to say that they never had any issues flying at altitude, then they aren't the best judge of their own performance.