Thanks. I have some pretty good sources.
My DD uses a wheelchair and we use the wheelchair accessible ride cars as much as possible. She also has
DAS because of other needs.
At WDW, the only time we have gotten 'priority' over other guests is when we were using Fastpass for an attraction like Jungle Cruise, which has a different accessible entrance. Because we were using Fastpass, we could enter right away. If we were using DAS or using a wheelchair without Fastpass, we would have gotten a Return Time.
The only times anyone else has gotten 'priority' over us at accessible entrances or boarding areas were situations like Toy Story Mania, Kimimanjaro Safari and Imagination where we were waiting for the accessible ride car and others who didn't need it went ahead of us. They do that to keep the area from getting clogged with people waiting.