It’s more a combination of things that made me wonder out loud... talking to yourself, struggle to digest what you’re reading, the ellipsis trains… also going to gamble on crazy high IQ, even if school grades didn’t reflect that. Your work might have, though… if you were interested enough.
Call it half hunch and half familiarity. Always said if there’d been a spectrum when I was a kid, I would have been on it. My daughter is ADHD. See enough of a thing, you start to spot it in the wild. ;)