I think when the GA scans your pass it does a different beep, and I know a message flashes on their screen, so I guess they are expected to do a quick visual check then.

One time I actually got moved because my hand was in a cast (broken thumb). I understood the need to move me, but they ended up putting an elderly couple in my place. As an in-shape mid-20 year old (at the time...still in shape now, just not in the 20's anymore ) I personally felt safer with me there than them, but I technically was disabled.