You really have to wonder if FRatSTN, Phileas Fogg et al have ever actually experienced the speed of getting through all the formalities at SEN. Plane to train platform at SEN with hand luggage only - as little as 5 or 10 minutes.
Transitting thru SEN isn't on my list of things to do!
I fully appreciate the ease of uncongested and well laid out airports but do SEN punters get around the M25 any quicker, do they not need to queue to pay the Dartford toll etc. etc. etc?
So if transitting thru SEN saves, let's say, 15 minutes then that is the only advantage SEN may have and, on the grand scale of things, 15 minutes (or similar) isn't very much.