I can completely feel what you are talking about. I even managed to run company which was part of large organization on CEO position.

I knew and realised particular problem years before I quite as no one acutally was aware of magnitude of my drinking.

However, I had perfect results and was highly functional even when I started drinking from moment I get out of bed.

Of course, depression ans anxious disorders are with me (I believe that it would not impact me so strong in case I were not drinking) today, after 5 years I sobriety but what the heck.

Therefor, I am quite sure that certain people are quite okay when drinking, they can be high-functioning, but really depends on lot of external factors.