Agreed. But the nature of the transportation system is also different. Unlike the boats and buses, you aren't bringing 50-100 people at a time to those 4 gates. You are only bringing 10-20 people (depending on capacity) every few minutes. So the spacing is different. Might they have to expand the number of turnstiles? Yes. But probably not as much as an entrance that services the hundreds coming in off the monorail all at once, or many bus loads showing up all at once. The resorts are huge, but the delivery system, while having a large capacity, is actually better spaced to allow for orderly procession through fewer gates.
Every Few minutes ? They could be as close to every 15 seconds, esp at busy times (morning/night). That's how often many of the big gondola systems depart.