What he does is very much real. One of his influences (and the person that recommended him for nanadan) is Isoyama Hiroshi Shihan who is know for is powerful technique.
Seagal Sensei is real.
I still wish Isoyama Shihan would have made it to the Aiki-Expo. I would love to take ukemi for him, or at least watched.
Isoyama is a great teacher and a good man, and if he thinks highly of Seagal sensei as a person and as an aikidoka then I think he has a reason fo it.
On a more personal note, I happen to have a contact with Seagal sensei, and I think he's a great man.