I was told as a child that I didn't have ADHD because I was able to sit quietly and read for long periods of time. I was only able to read for long periods if it was a fantasy novel. Now, in my 40s, my doctor was amazed I'd never been diagnosed as, according to them, I'm "textbook."
The "I just read a 500 page book in one sitting and now I feel empty inside, like a deflated balloon. I should maybe eat." hyperfocus has always been my style.
Also in my 40's and recently diagnosed. I filled out a questionnaire, and the doc asked a few surface-level questions, then proceeded to describe my entire childhood-young adult life. He was not wrong on any detail.