My reading of the article is that he wasn't actually the bartender when he initially entered the bar. He says that "the only seat left was behind the bar," impl

My reading of the article is that he wasn't actually the bartender when he initially entered the bar. He says that "the only seat left was behind the bar," implying that he was just another patron of the bar. If that's the case, the attitude of "don't get used to that" is because as just another patron, it's not his job to get other people drinks.