He didn't need any other accommodation. He just cannot be on his feet for any extended period of time.
I was asked at Space Mountain.... Which has stairs, in the "regular line". So, it was odd that I was asked for the GAC at the one ride that he definitely couldn't take the wheelchair through.
My Personal opinion is that it is good practice to ask for a GAC even if a person has a wheelchair. I believe there's a lot of chairs rented solely for the purpose of line cutting.... I know families that rent a wheelchair just for this purpose.
WDW's policy is that guests using wheelchairs and
ECVs don't need a Guest Assistance Card to use the accessible entrance ( which they call 'Mobility Entrances' .
My first suggestion is to get a park map for Guests with Disabilities - there is one for each park and in most parks, you can find them along with the other maps.
You do not need a GAC to use those entrances with a wheelchair or
ECV. That is why they made those maps. If you are told you need a GAC to bring the wheelchair in line, check the map first. If you are at the Mobility Entrance, showing the map usually takes care of the situation.
I actually had a CM ask for a GAC at Dumbo and as I went for the map, she said, "oh, wait. You don't need a GAC. I didn't notice the wheelchair".
The chair my DD uses is bright fuchsia and had a sparkly blue seat cover - so hard not to notice.
CMs do sometimes get on automatic pilot and ask automatically.
If it doesn't, then ask for the supervisor. We had a situation once at Splash Mountain where we had waited in the line up to the point of the stairs. Despite the gate with a wheelchair sign and DD's wheelchair, the CM would not let us go on because "that would be cutting the line". She continued to argue with her supervisor , but did finally let us through ( complaining the whole time).
We also had a situation where we had Fastpasses for Pooh and the CM said we needed a GAC to come into Pooh. Another CM heard and corrected her.
I feel strongly that it's important to get these situations corrected by showing the map or getting a supervisor involved.
If people with a wheelchair or ECV and no othe needs 'present' a GAC that says they can use the wheelchair entrances, it just confirms to the CMs who are not following policy that they should not let anyone in line with mobility device unless they have a GAC.
Showing a GAC when one is not needed may help on that particular time going in, but Makes it more likely the next guest will be asked for one also.