Re: Why isn't this showing Aikido as effective?
not Kevin, but here's my two cents.
Occassionally I'll catch an aikidoesque pin, face down controlling the arm vertically. Never on anyone with decent experience - even if I get the position they generally roll out before I can lock it in. Part of that is I think to do with their ooda loop - groundfighting is predicated on rolling your body around, twisting it in and out of good and bad positions. Where as standing there is a possiblity perhaps to get more advanced on the pin while they still think it's a standup game. who knows.
I will say though that the BJJ move known as omoplatata is pretty much an aikidoesque pin - the key difference being that it is done with your legs pinning their shoulder, not your arms - which in actual fact frees the arms up to control the hips and prevent the rollout.