When I did my initial altitude chamber ride in the early 70’s, it was at Beale AFB in the SR-71 altitude chamber. At that time, both RD (rapid decompression) and a gradual ascent were simulated along with task performance degradation examples which could be funny, at times (acting goofy OR outgassing). As you opined, the RD was a major event taking the participants from – I think – ~10K to 43K almost instantly in an interlock chamber. You would notice that. For me, I learned that my nails turned blue and I started feeling very warm and comfy prior to loss of ability to function. Also, I have a complex ear canal which is very tough to clear with the valsalva maneuver. The gradual ascent IS far more important and insidious IMHO.
On a couple of occasions, I’ve had to climb my 172 up very high for weather reasons. Knowing my personal hypoxia symptoms made a BIG difference.
I would advise every pilot who flies up high to take altitude chamber rides or that new FAA thingie they have in their hangar at Airventure. I’d also opine that age IS related to ones ability to deal with hypoxia.