And if PubMed isn't your cup of tea, just head over to https://www.reddit.com/r/keto, unless you think those ~125K subreddit members are just lying.
Not all calories are the same. I myself lost almost 40lbs on the keto diet (~200 to start, now around 160lbs). 31, male, sedentary IT worker. NO EXERCISE. I eat everything except carbs (fruit, beer, anything with sugars).
Alcohol doesn't contain sugar. Rather, it replaces glucose in the blood and can be used directly as a fuel without any conversion.
This is unlike in low-carb diets, where fat must be converted to a fuel (via gluconeogenesis) before cells can use it as energy, and this conversion itself takes energy.
Effectively, alcohol reduces the benefit of low-carb diets but doesn't necessarily increase the insulin response as would a high-sugar diet.