On busy, core routes like the 2 and 38 then it matters, you wouldn't exactly want a Solo to appear on a peak time journey but for a service like the 31 which is a very marginal service then single deckers are more than adequate. I've used this service a few times and it seemed to pick up very few passengers and definitely not enough to fill a decker so why it'd need a decker is beyond me.
Fills a decker at peak time for sure . Better to keep decker on the route all day , as they do .