The wait time between buses in the middle of the day can be as long as 30 minutes (we have waited longer actually). It sounds like they estimate travel times of ten minutes, when travel taimes can take longer. Often driving tim to get to MK takes about 15minutes. I'd put the typical times more realistically at between 15 minutes and an hour.
Last year, it took us over an hour to get to MK from POR at 5:15pm. Not only that, but getting on the bus was a mob scene. If we hadn't been agressive (we were some of the first people at the bus stop too.), we would not have gotten on the bus, period. Most the people at the bus stop did not get on that first bus, and anybody who wasn't wating at the main bus stop did not get on that first bus. And let me say, some of the late comers were really trying to shove their way onto that bus!
It can also take extra time to load/unload wheelchair-bound guests. I'm not being critical, simply stating facts.
If there is long line of people waiting for a bus, your wait time might be longer too - like at park closing - since you'll have to wait for the next bus.
Another trip from AKl to DTD took 45 minutes - thattime, it wasn't the wait that was so bad, it was the driver. He was driving REALLY slowly. Luckily, the bus to our resort form DTD was much better.
Having said that, the above are more exceptions than the rule. If you are lucky, then most bus trips will only take about 20-25 minutes. Just don't count on it when it comes to getting to a park in time for ADR's.