Excess waiting time Luton airport parkway to west hampstead

I was on a class 700 (8 car) on Saturday evening, the 1846 from luton airport parkway to sutton. I was travelling to west hampstead and what i noticed is that the train seemed to arrive at every stop along the way a good 2-3 mins early at every stop, resulting in longer dwell times, which probably slows ones journey down. Is there any reason they are timed to wait for so long at each stop?

I suspect this may be highly likely to do with the fact that the timetable is still produced to match the perfromance of the 319s, but any info would be helptful