Not defining self defense and then claiming to do self defense is a cop out and to provide ethical training you need to specify what you are actually training and what sort of progress you can expect from training it.
Although, this is your thought pattern, it also contradicts what you have written, yes you can defend yourself without training, and yes you can arrest someone with little training, but without training, your chances of defending yourself diminish, this is why the majority of people take up martial arts. As reqards to effective self defense, your going around in circles, any training is better than none, pressure testing through sport or contact sparring is the best way to test ourselves other than going out fighting week in week out, just because we do not record this by way of 17 and 0, with 15 knockouts or submission, or have the stats of, in 200 fights, there was 95 knockouts, 48 submission, so lets all train powershots, and submissions, because our stats say thats what works this week, so if you dont train it, your wasting your time.
I am sorry, I never recorded my total amounts of wins etc, and how the fight was won, but I was busy fighting.
But self defense instructors and the bulk of the industry choose to keep this vague.
This though, I do agree with, there are far too many in my opinion, and a lot of 25 year olds opening self defense schools, and claiming to have 10 first dans in 10 arts, this is worrying as there will be a massive drop in quality of techniques taught, butbthen this is my opinion, I have no evidence to back this up.
Now if you were to ethically break down self defense in to a defined purpose you would be able to see and gauge what you are learning and whether or not it is having any effect.
You mean something like, person gets fit, person improves core strength, person learns to move in a self defense minded way, person learns techniques to help in self defense, person spars, person learns what things work for them, and what dosnt, person continues regular sparring, learns how to adapt techniques, and combine techniques, person improves distance and timing, person becomes better at adapting to different size people, with different strength, speed, ability, persons confidence grows, person looks for new skills to add to their repitiore, person continues to grow, I could have rambled on a lot longer.