What he means is 'I thought everyone drinking copious amounts of alcohol was working, because drinking multiple bottles of wine whilst working is perfectly normal in my world'.
FFS. They were presumably not working, because they were pissed. If they were working when pissed, that is not really better.
If I had seen my colleagues drinking loads of booze, I would have thought they had stopped working and started drinking. Obviously, because my workplace, whilst laidback, is normal and staffed by normal people who take their jobs seriously.