Good. It looks like we are in agreement in that the specific level of risk is virtually unquantifiable, and certainly in terms of anything meaningful to the layman.
"The suggesting that participants accept the risks of an activity is a fiction."
Participants aren't "accepting the risks" however so much as accepting that participation is 'risky' as deemed in law. Just a matter of risky or non risky. I don't see why it needs to be any more complex than this.
I accept my pole dancing experience will be risky. My gorgeous pole dancing instructor has advised me that as a fat old man , I could well slip from the pole during my lesson and do serious injury. She actually did this for the whole class and also had me read a waiver form, confirm that I understood it and had me sign it.
Its irrelevant how this level of risk compares with canyoning or even golf. All that matters is that I am reasonably warned of the potential 'riskiness'. If I accept this then any unforeseen outcome was agreed to be accepted by me as an informed adult.
Taking your Aunt Mable for a flight in a Jabiru or Cherokee may not warrant a waiver form but she certainly deserves to be told that flying certainly has an element of risk above everyday activities (even if this is arguable). Ideally you would do this in the presence of at least one other.
I used to advise passengers and students that I had a greater risk of being killed by a little old lady reversing without looking, out of her parking spot in a country town main street ..as I almost was a couple of times. I dont say this anymore as that risk comparison wouldnt be accepted in any review.
LD