I understand what people mean when they say it's good that the disabled queue will no longer cause congestion, but... it's a claustraphobically narrow pathway with a steep flight of stairs at the end... in other words, not a way I'd be happy to see disabled guests access the ride. Obviously, wheelchairs will still need to use the lift, as well as people with any other disabilities that mean they cannot walk up steep flights of stairs. It might ease conjestion a little bit in the photo sales unit, but I don't think it's going to be noticeable enough for it to pay off.
To be honest with you, I agree with the theory that this is a scheme to try and sell more Fastrack tickets. As guest numbers will presumably grow with the additions of major coasters every three years, the queues will gradually rise, and the park will ultimately sell more Fastrack tickets, making them more moeny. And just to really boost their profits, Merlin will set up little schemes like these.
You'll often notice that rides, particularly at Thorpe, have queue times advertised as much longer than they actually are, and while I am sceptical about this, and entertain the possibility that it could simply be mistake, I do believe that this could possibly be another subtle way of encouraging people to purchase Fastrack.