I don’t believe for a moment that an easyjet manager said “It takes longer at Luton to process a planeload of our passengers than it does to process a jumbo-jet planeload at Gatwick. If he did then he would be criticising his own company, as easyjet does their own handling now.
It is also worth noting that Luton is only 30 minutes by train from London and that 9 trains an hour call at 6 central London stations compared to Stansted’s branch line service which takes 45 minutes. Even allowing for the shuttle bus it is still quicker getting from the aircraft to Central London from Luton, as there is no train to wait for to get from the stand to the main terminal.