Absolutely this. A normal range of feeling / experience isn't a "bit of a disorder" ... it is no disorder.
Feeling like you need to wash dirt off your hands before eating isn't a "bit of OCD", that's normal.
Worrying irrationally so much about clean hands that it ruins your life, leaving you crying from normal tasks like cooking ... every touch of a surface triggers fight/flight ... is a disorder.
It isn't the mechanism that's important, but the impact and motivators.
Same with ADHD. A bit of being inattentive or forgetful or whatever ... isn't a "bit" of the disorder that also contains some of those behaviours in extreme.
In many cases it is not a differing underlying cause but simply the same thing further out of balance. Psychiatry diagnoses are essentially never based on a mechanistic explanation and I challenge you to come up with an actual binary change present in those with adhd and those without besides the latter having somebody put that label on them.
An equivalent is saying everyone has trouble walking sometimes when we're talking about someone who limps and needs a cane.
The symptoms are not the disorder and don't come from the same mechanism that causes normal people to have difficultly paying attention sometimes.