But it is also be true that the insight "most people loose ADHD by adulthood" is in itself kind of flawed as people can develop coping methods which can mask the ADHD. If there's a significant people complaining/reporting then, it would be something to look into.

People are more open about having adhd into adulthood as compared to in the past where it might have been seen as a childish thing and hence undesirable to report. And not a problem enough to report it to someone who could help with that.

These are assumptions based on personal and shared anecdotes, so I guess you could still argue what you said is right.