It would be more meaningful if the TOC and which station's gateline(s) were involved was publicised. Also, at what time(s) of day the measurements were made.
St Albans has two of the busiest gatelines outside the London zones and my observations are that those who use phones for their tickets are fiddling with them as they walk across the footbridge and along the platform. I normally have a CCST which I can take from a card wallett without even looking at it, (I always put it in front of my ENCTS pass). Any sorting out, e.g. outbound tickets/other cards, is done on the train and the ticket doesn't need any screen tapping because the screen has gone to sleep, or the lock has kicked in after 30 seconds! Contactless, would also be much quicker as that can be accessed without digging around. My phone is still there, ready for calls, surfing, listening to radio etc., but none of that gets in the way of passing through a gateline.