I hope it is only 20 years!
O'Sensei is supposed to have called it the 20 yr technique himself because it took him this long to perfect it.
I think the difficulty arises because in it's basic form it appears to be a whole arm strike to the throat like you'd get in wrestling (a 'clothes line'?). The difficulty (especially in irimi versions) is getting ukes forward momentum into a very tight circle where it goes back against himself and down to the floor.
I've been doing Aikido for 12 years, and although I can do it, it definately isn't the blending technique that I would hope for.
Only 8 years to wait?