In my opinion, learning to use a non-locking knife will benefit a young person most. He will treat the cutting edge and tip with more respect if it can fold back on him with improper use. Probably the best building block in usage for somebody who wants to keep all his fingers long term.
As to your question of such a knife as a self defense weapon, I always have my fingers crossed that the next James Bond or Jason Bourne movie will feature the good guy making do with such an option in a knife mismatch with the bad guy![]()
Noooo we don't want that! Next thing we know, Swiss Army knives will be banned as weapons.