Sometimes memories just take some time to process, especially if you're exhausted. Given a few nights of sleep, I bet this kid will start running the events back through his head more and more, and thinking about bits of it he wants to talk about.
Yeah this is what happens with our kid (who, admittedly, has ADHD so maybe he's a bit unusual). The first day or week after a cool experience he's pretty meh about it and won't volunteer much in the way of thoughts or feelings and then suddenly he'll realize it was real again and all of a sudden he won't shut up about how cool it was! Then eventually he settles down into a steady pattern of "hey remember when we did X thing wasn't that so cool we should do it again" which is my favorite phase because that's how I know what he really likes that stuck with him. : )
Hey, c'mon now! You can't be going around saying people with ADHD are unusual. Have you SEEN society lately? Pretty sure everybody has....IS THAT A BUTTERFLY????