I think the problem here is that people are confusing terms.
In the Al Lutz article he was not talking about ECVs, but GACs. GACs are Guest Assistance Cards for those who have needs not readily apparent to CMs. There are different stamps on the GACs which lead to different accommodations. That is one problem with Lutz's article, that it conflates all GACs, when there are several different kinds. There is a GAC that allows you to wait your time outside the line. Basically the CM writes on the GAC that you used it today and gives you a handwritten FP to return. Let me stress that this is not an accommodation given to everyone with a GAC. Some GACs are to avoid stairs, you do not need to avoid the line to be accommodated. For this GAC you wait in the standby or FP line and show the GAC to use the accessible car.
In my experience those in a ECV do not skip the line at all. I took my ECV through the standby line and through the FP line. The line is fully accessible. They do separate you at the very end and load you in the accessible car, but if anything this line was longer than the normal line.
The OP says they went through the single rider line, which is interesting. I wonder if they used the accessible car?
At any rate, I have no idea what Al Lutz was talking about in his article when he said all the GACs were going on RSR anytime they wanted. First of all, there isn't a single accommodation for a GAC. Second, even if you did have an accommodation to avoid the line, you still have to wait the time of the entire standby line. When they write the FP, they write it for the length of the standby. AND they write on your GAC that you already used the accommodation for the day. You can't just sit and do loops on the ride.
This was definitely a case of Al Lutz writing about something he had little knowledge of. He should have researched more before conflating all GACs and accommodations.