I have seen the rule enforced on both the busses and the rides. There are likely drivers who don't enforce the # rules, just like there are drivers who don't enforce the you can't stay on the ECV rule. The problem is that this perception is applied to every ECV user, especially those who don't "look" sick and the verbal abuse of the ECV user and their families is common. The snide remarks and dirty looks are rampant. Thank God Disney doesn't treat us like second class citizens (for the most part) because the other guests do and I am sure that many aren't even aware that they are doing it--they are so convinced that people on ECVs are gaming the system for perceived privileges that they feel that the verbal and emotional abuse directed at the ECV user is justified.
When the lines are mainstreamed, ECV users use them. They wait just as long, and often longer, than the able bodied, but still face ridicule and abuse because they are loaded before the people around them in line.
My point is that to have equal, not better, access on both sides means that if the ECV party can't board with their entire family, neither can able bodied families. That isn't going to happen, nor do I expect it to, but at the same time, it is not unfair to allow the person in the ECV to travel with their family when the able bodied are allowed to travel with theirs--or make the *choice* not to. ECV users are not given the choice. If there were a way to board the ECV or wheelchair safely when the bus is partially loaded, it would be a different situation, but there really isn't. Not only do the seats need to be raised to park the vehicle, but there has to be maneuver room to pull it forward and then back it into the space, and to lock it down. Disney has decided that it can't be accomplished with people already on the bus, and I can't say I disagree. People would get hurt, no matter how skilled or careful the driver of the ECV was.
I think part of the issue is that you can see how many people are in the group with the ECV, but you can't with the people standing in the lines, so it is thought that ECV users travel in huge groups so they can have the advantage of getting on first. We have even had people try to tell CMs for rides that they were with us so they could get in the accessible entrance. I told the CM that no, they weren't with us, but I should have let them come along. They went through the line and got on the ride before we did.