I also disagree that an ECV makes one eligible for special line status, at least for the attractions where the ECV can fit through the queue (and the queue does not involve steps). If the queue is accessible, then there's no reason AT ALL that someone should be afforded special treatment such as not waiting in line.
I realize you're first sentence is specific to ECVs and the second may flow from that, but just to be clear:
Any queue that is accessible should indeed be used by someone in a Wheelchair or ECV to the point where they need special assistance to load/transfer, but since different rides have different procedures for load/transfer from wheelchair/ECV, it may not be feasible [or fair] to require the wheelchair-bound guest to wait in line and then wait longer still when they reach the front for a particular accessible ride vehicle. So conceivably there might be factors other than accessible queue that come into play.
There
also are legitimate medical reasons for individuals to be allowed to avoid waiting in line. Using myself as an example: I have a number of problems with my feet, I have had all but two of my toes amputated and have a full-thickness skin graft on one heel, both as a result of frostbite. As a result, although I can walk distances with minimal risk, I have balance problems standing in lines and that creates problems with blistering on the skin graft. I use the Guest Assistance Card when I'm in the parks, but only when ride queue wait times extend beyond 30 minutes, which is approximately my limit before I start having serious issues that can ultimately put me in a wheelchair for up to three weeks.
Outwardly, there is nothing about me that would provide any clue to a casual observer that I have any of these problems. Interestingly though, because they also amputated all of the fingers from both hands and moved three of the toes that are no longer on my feet to my left hand... People see my
hands, which have no bearing on my need to avoid lines, and decide I'm an "acceptable" candidate for "special treatment".
A fair statement is: Don't judge someone's situation until you've walked a mile in their shoes, if they have shoes.