I change a potential shoulder injure for the ability to avoid a beheading any day of the week. And there is always someone who thinks his/her pins are awesome...
[Link deleted] 10:50 to 11:55
BTW, people is escaping from omoplatas (which is a thighter pin) rolling and nothing happens.
That video doesn't demonstrate anything about how rolling out of a pin is correct technique.
Just because nothing has happened to you yet doesn't mean it won't.
I have ,many times,adjusted a pin in the past for some one I knew wanted to roll out of it to allow their shoulder rotation. You can't take nage's corporation for granted.
The fundamental does not allow for flipping out. A proper pin has the uke's ballance from the cut. There is no time, nor is there footing for uke to gain rotation. If he tries to he is likely forcing rotation from the top portion of his body, not generating it from the ground up. In which case he would not be able to gain enough rotation fast enough, which could cause him to plant his face, shoulder, neck..ect unless his nage was helpful and seen that he was trying to gain rotation and helped him along for his own safety. Some school might practice this corroborative nage style by default for uke's safety, my school doesn't. The goal is always the ground.
Also there are many trajectories going on here. Not just the movement forward that takes you down to the mat. There is motion taking you around nage's center, out to the side. If you are forcing rotation forward, and nage has motion heading out forward, down and to the side you are fighting against his movement, which hyper extends the joint a bit. Spinning with a hyper extended join despite your dispute is dangerous. The join is weak in that position.
If your defense is that you've constantly being flipping out of pins, I'm sorry, those pins aren't pins. They are either done poorly, or nage is feeling merciful. Also sometimes Nage will take a pin into a projection throw... not the same thing as a pin.
In my humble opinion: I'm not doing Aikido for the sake of role-playing, or cost-playing here. In feudal Japan, yeah you might lose your head...but luckily this isn't feudal Japan. I've no delusions that I'm a Samurai. The threat of destroying your shoulder and ending your martial career is far more likely in the modern age than an imaginary Samurai beheading you.
Also, tighter pins are actually easier to gain rotation in, in my opinion. It is pins that take you out wide that robs you of your footing and rotation. Tight pins, even pins that go straight down, are extremely easy to spin out of... for me at least.