Firstly ['covert stuttering' ](https://stamma.org/about-stammering/stammering-facts/covert-stammering)i.e. passing as fluent is a thing. I had a severe stutter, but over a long time and a lot of speech therapy have managed to get to a place where I can maintain a 'covert' stutter. This doesn't invalidate my experience with stuttering. Secondly, you don't know whether or not someone has ADHD - and regardless, these are just attempts to be relatable, a very basic human socialising tactic, so I wouldn't really put too much weight on it tbh.