I liked to call myself a "high functioning alcoholic" as this made me feel better.
Now that I am in recovery, I see that I am no different than any other alcoholics. I am one drink away from being back in my old life.
From what you are describing, I wouldn't say that he is a high functioning alcoholic at all (e.g. lost his job, health issues, weight problems, multiple detoxes).
I would ignore the labels. He is an alcoholic and therefore not functioning too well.
I just don't want you to cling to this label if it in any way justifies his drinking.
Alcoholism is progressive. Soon, if he keeps drinking, his downward spiral will accelerate downward.
I just hope he can get off before it gets too low (and remember, you CANNOT do it for him).