I agree completely with those who have noted that under stress we revert to what we have practiced in the body - heck, most of us who have trained any length of time have saved our asses by automatically rolling or falling correctly when we have slipped or gone off of bikes, horses, stairs, etc.
What I have to take issue with the OP is the assertion that aikido uses "fine motor skills."
Fine motor skills means the manipulation of small objects with the hands - it is embroidery, cardiac surgery, tying your shoes, watchmaking: all the things that require manual dexterity and can be done while standing still or sitting.
Aikido should never rely fine manipulation with the hand, but on whole body movement originating in in the center.
Many students rely on catching punches (which isn't necessarily fine motor skills, but still difficult), hand positioning, etc. Aikido does require to a degree, some dexterity which from what I've read and experienced, can be destroyed in no time. I'm not saying it relies fully on fine motor skills but many of the techniques rely on skills that are harder to utilize as opposed to a simple throw or punch. That's not to say it's ineffective, just merely an observation. But you do bring up a point I haven't really given much consideration.
I'm not saying any of what's been said above to be untrue. I'm actually fascinated with some of the stories and I know that it does become instinctual in time, but it's still impressive to hear stories.
So while I still see Aikido as an effective art, it's not as practical as the things I've practiced previously so I wanted to know how Aikidoka responded under pressure. Great stories so far.