Let a good judo player, wrestler, karate person grab you and "breaking" their grip ain't so easy. Don't even get me started on a good aikido person or DRA person. Some of the good aikido people can grab you and prevent you from doing anything. Just when you thought your tenkan was good...
As Alejandro noted above, our Sensei emphasized always
breaking the grip as the first
thing. Then re-grab the grabber and apply as you describe. Mochizuki Sensei developed a full set of escapes for every kind of wrist grab, arm grab, shoulder grab, choke, bear hug, waist hug, etc.
A truly mighty and crushing grip is important for developing aikido and anytime someone gives me an excellent grip, I'm glad for it. But not many people can actually do what Chris demonstrates on his video. Very few would last half a second without serious wounding.
And, again, the main reason the wrist grab exists in aikido is that it's a very common attack against an unarmed person--not because the samurai may
have once used it that way. Otherwise, we'd have to explain how a bear hug was used to prevent nage's drawing his sword, or how a rear two-shoulder grab was developed for the same reason. Second, working from a wrist grab is the easiest way to develop the reversals and general mechanics that will apply to all other uses of a technique, including strikes and the more general body controls such as bear hugs, waist hugs or chokes.
Of course, any attack could be related in theory to controling an armed samurai, but I note that thousands of people have learned to do the techniques without that in mind and at the dojo where I trained in Japan, such an explanation was never used--especially for teaching.
Best to you.