To be clear, I am ADHD (executive-type) and am empathetic to my friend. All considered I am quite fond of my time spent with them. But in regards to developing a model for ones character I don't think it is very helpful to allow disabilities to shape them. It is simply impossible to share the individual essence related and is better understood through the manifestation which is ultimately shared. And regardless I would hope they would seek this diagnosis as a function of their own introspection according to my account of the phenomenon, not some extrapolation. [0]

To engage with your curiosity of their situation though, they spend a lot of time at poker tables, sitting for 8+ hours. I would assume this is not a common enjoyment for most ADHD minds. From my experience as soon as I'm out the action for a string of hands I'm completely checked out of any rigid strategy. Now sit me at a blackjack table and I can crank hands until the morning! But here I am being fed action and drinks basically on demand.

[0] I'm just thinking out loud here, not accusing you of making any claim related

that's not ADHD. People with ADHD would improve - it may take a LOT of time, but it will happen. Quite often they will go to the extreme and come in way too early. My bet would be on Cluster B personality trait e.g. lack of empathy and constant need for attention and validation.

ADHD frequently co-occurs with other conditions.