Maybe, being a vain he had dropped the people off earlier on through MT and had ranged to pick them up, and by pure coincidence got another job to their jut on time.
Maybe, just maybe, since it was a van, there was more than 4 passengers and there was only saloons on the rank,
OR maybe, just maybe, when the passengers going to Guinness Robhouse, were getting out, the intending new passengers asked can they pay by MT, maybe, just maybe.
Anyways, thee is no rules about picking up in close proximity to a rank, just another gentleman’s agreement between taxi drivers years ago. Just like the don’t overtake someone who has their light on and don’t pass another taxi from Whitehall while heading to the port