It's not easy to explain, but I'll try. You can concurrently load more than one gondola vehicle at a time. So While they may say 20 seconds to load, there is likely a window of 60 seconds or more.
So lets say you have 6 cars coming in, the process will overlap. You will have multiple cars in different stages of loading. The gondola may very well spend close to 2 minutes in the "station" as part of the process. However, every 20 seconds a car is sent out of the station, hopefully full to it's capacity. It's an omni mover. Not every car will be to capacity 100% of the time. The whole system could slow on occasion, it could stop briefly. Even in those cases it will still likely be more efficient that buses. Like anything, when you exceed capacity, it's going to be a kill joy. However, I bet we will find it's capacity is greater than the conditions 90% of the time. You'll walk up, and board. You won't wait but a minute, and they'll you'll be moving to your next spot.
Which style they use and the loading process is highly variable. Scooters and wheelchairs will be a challenge, but nothing too crazy to deal with.
It will be light years better than the busses, boats and monorails. Will it be perfect, no.