The aircraft are loaded with cans. If he took his own chair to the aircraft he would then hold up the entire flight whilst his chair is then loaded under the terminal. The cans are not usually opened on the tarmac due to security practices. I guess it could have gone in the bulk hold but there is always more of a chance of damage due turbulence in the bulk.
It screams out publicity scam to me. After walking the track then CHOOSING to transport himself through the terminal and out to the aircraft you wouldn't think that another couple of hundred meters would matter.
This bloke has made a class 1 fool of himself in most peoples eyes and unfortunately conforms to the lowest common denominator of airline pax these days, disabled or not.
Doug.