Here's
a link to the thread about stopping SAP at Disneyland (which was actually changing their program, not totally eliminating it. Also, here's some further information about GACs.
The GAC isn't given based on diagnosis, so there isn't a "Yes, a child with SID will get one" or "no, they won't" answer; it's given based on needs.
To request a Guest Assistance Card (we call them GACs to avoid typing so much), go to Guest Services in any of the parks with the person with a disability and explain your needs. Just saying, "My child has ADHD or SID" does not help much, because some people with that diagnosis will have minimal problems waiting in line and others will have lots of problems. The CMs are not medical people and may not know what types of difficulties people with specific disabilities/conditions might have. You don't need a doctor's letter to get a GAC, although some people feel more confident asking for one with a doctor's letter in their pocket.
You need to be able to explain what sorts of behaviors/problems you expect to encounter. The GACs have different messages stamped on them, depending on what the needs are. GACs issued in one park are good in all parks and are usually valid for your entire length of stay (You don't need to get a new one each day). GACs are usually issued for the person with a disability plus up to 5 members of their party - there may be times when you are asked to split into smaller groups because of attraction capacity in the special needs area for that ride.
In general, people who use wheelchairs or
ecvs don't need and won't be given a GAC because just having the wheelchair/
ecv alerts the CM that they need an accessible entrance. If that meets the needs, you don't need a GAC. But some people need a quieter place to wait, a place out of the sun, a place away from other people or to be able to bring a stroller into line and have it treated the same as a wheelchair. The GAC is a tool to alert CMs of that sort of invisible need. It is not meant to (and usually won't) shorten or eliminate your wait in line.