Re: final lock doesn't work
I may be retreading ground here, but I'll chime in anyway...
To be frank, I too have often wondered about the utility of immobilizing pins in Aikido.. but from a somewhat different perspective. I have often wondered what the purpose of a lasting pin in a non-sporting art is supposed to be.
In a multiple attacker situation, a lasting pin is pretty useless. Even a brief pin is fairly pointless and probably dangerous. I'm sure that there are people who can pin more than one person at once, but I've only seen that done once in an Aikido dojo, and it wasn't taught or meant to be lasting, and that is well beyond the skills of even (I'd guess) most BJJ people.
If the person has a weapon, taking the weapon and/or destroying the person's capacity to attack will be the priority, and after that, the pin is less interesting. If I've got the knife, why do I need to pin them if they keep attacking?
In a lethal force situation or other situation where you're willing to inflict serious damage, a lasting pin is likewise useless. Just do a brief pin to a break. Why would you not just break the person if you can, and move on from there in case their friends arrive?
If you decide to simply restrain someone who is attacking you and you're one-on-one, what's next? Presumably, you send someone else to call for help, or you cow the person into submission by the force of your personality or whatever... Those both sound like weak answers, and anyone who is around to get help would most likely be able to help you smash someone struggling out of your pin, even if you need the help. Likewise, you can smash them yourself or break off a piece of them if they try to struggle out from the pin.
I've had people struggle out of my Aikido pins, typically while my hands or other weapons were inches from their eyes or other vulnerable places. If I was really worried about them escaping, I would have done something more painful or permanent to prevent it.
If you're in a conflict with someone you don't want to damage (a drunk friend) avoidance is probably better than risking pinning for the long term and the potential damage that may incur, or having to wait until they sober up.
I guess that the only real use I can see for pins is to immobilize someone temporarily in a police-like role, or for this type of "I have weak, near allies" situation I mention above. But a policeman would be able to handcuff the person even from an Aikido pin - handcuffs are a more effective pin overall, even than a BJJ pin.
There are I suppose situations you could imagine where a lasting, non-damaging pin might be useful, for a time at least.. but I still don't imagine anything like that being common, and there are other skills sooner in the encounter chain that it would be more advantageous to practice more thoroughly.
That said, what's the point of spending a LOT of time teaching lasting, non-violent pins in a non-sporting art and expecting them to be effective 100% of the time?
There are more interesting and relevant things to teach, unless you want to demonstrate submission for the purposes of a contest (like BJJ or Judo), or you want to bully someone, or unless you just want a pretty way to end your technique.
Until I can get the beginning of my Aikido technique to work correctly, why should I worry about the end overly much?
Just my opinion,