An ambiguous claim, a safe statement by its ambiguity. 'Many' civilian pilots are prior military pilots, and all of them have had it, and have it around every 3 years during their military flying careers.
Most professional pilots are acutely aware of the effects of hypoxia, because it is constantly trained in initial and recurrent training for every aircraft and crew position change.
If that were true there would be no need for altitude chamber training, "mostly".
You're beginning to sound like a WH spokesperson, airline pilot version!