What is the official policy if the kid is tall enough to ride but just does not want to?
One of my twins does not like roller coasters. For 7DMT, twice on our last trip we went up to the CM at the entrance, said we would like to do rider swap, they took a quick look at DH standing with her and gave us the pass.
Another time, the CM said she had to go through the line with us and we would have to do the swap there. I must have stared daggers at him because another CM came up and said "just give it to them, but that isn't the policy." I wasn't sure what she meant but took it and went on my way.
"Official" policy? Hmmmm . . . .that's a good question. And one that people on this board will have lots of different and aggressive answers to! The problem is the policy on what happens is someone is tall enough to ride but doesn't want to isn't clear. In one place it says swap is for people who don't want to ride. In others it's for those too short. In practice - it's often a judgment call made by the CM manning the line and seems a bit inconsistent. I think the younger the tall enough child is, and the closer to the cutoff, the more likely they'll do a swap anyway. But if you have a 12 year old, 4' 6" child who doesn't want to do 7DMT, I think you might have a harder time. The big issue with swap is that a child too short is not allowed in the line at all even if not riding. For SOME rides (as your CM noted) if a child is tall enough but doesn't want to ride, it's possible for the child to go through the queue, "chicken out" at the front of the line, and have the CMs arrange a rider swap there. That isn't always possible, depends on the how the ride loads/unloads, but I've seen it at many. Again - up to CM discretion but even on rides without a "waiting area", they can find a way to accommodate.
Wish I could give you a more definitive answer, but can only report based on personal experience (I have twins as well - one a daredevil and one not!) and all the other reports from here.