I'd bet the player who summons the mount will be "inside" the main body (or in fact, just invisible like with the alchemy dragon) while the riding player will be grapped by the claw, showing the race model's falling animation.
From looking at it I guess they're giving us the mount that Overspark uses during the Operation: Shieldwall daily A Kind of Magic. He flys in on it when you call him via his scouts. When he uses it he's shown standing on top of it with a slight glow from the top between the rotors and the scouts are picked up in the claw and dropped on the target.
I'll take this opportunity to say that it's extremely doubtful that the claw-copter in the picture I linked will actually be the mount. It will obviously be a brand new model loosely based on that old claw-copter.
I, for one, have absolutely no doubt that Arcane, as an entire spec, in both PvE and PvP is going to end up in the toilet throughout the entire MoP expansion. You can bookmark this post, screenshot it if you wish, but you will see that that statement of mine will stand the test of time.