Yeah -- my expectation has always been that they won't aim for 100% fill. I would guess they'd err overall on giving people some breathing room and granting preferences as long as this thing is as efficient as it is billed to be.
This is the Disney way. You don't over stress efficiency where there is little to gain vs what you lose. It's why Disney will send out vehicles with empty seats. Or tend to let small children go without strangers next to them, etc. They tend to err towards customer sentiment. On high demand days, they may spend more time filling those seats, but they aren't going to stop dispatch to do it. On days there is less demand, they may be more lax and spend less time/labor on it.
Its why it was said before... Disney won't bother stuffing the box. That does not mean tho that Disney will not put people together.. it's just that keeping parties separate is probably not the highest priority.
I totally expect the count per cabin to be based purely on the queue at the time. When in high demand times they'll simply emphasize putting groups together more.
This is easily accomplished if grouping is done by the platform person directing people to a cabin as you approach if they can have people enter a cabin after it's passed the first load point. "how many in your party? Ok, please enter this cabin" Thus the stuffing can be done entirely dynamically.
But if they don't want people trying to catch up to a cabin that has already passed the first point on the platform.. they'll have to group people before they enter the platform. And again, if the area is large enough to move around, a grouper can easily work on arranging the line as needed.
Personally I think there is good reason to use the 'multiple rows/stalls' method. Why? Because trying to get 8 people to move together can be difficult if they are not triggered all at the same time. And having multiple groups of those sizes move together is even harder.
Think of the classic 'traffic light' delay problem. For every person in front of you, there is a delay between when they get the signal to go, and them actually going.. and then the person behind them does the same thing, etc. This causes a cascade of delays making it hard to keep a line moving. And since you are trying to move multiple people in a group... this problem is magnified.
So to create a smooth loading of groups - you usually have to stage them and make it easy for them to all go at once.
