Although it's hard to conduct and find accurate research about blackouts, it's been recorded that the blackout stage is usually preceded by very rapid drinking at very high volume: drinking a very large amount, very quickly. Which is not the way people usually drink, even when they are an alcoholic. And that the speed and volume affects the brains ability to make memories, hence the problem people have remembering.
Being in a black out drunk doesn't mean you are unconscious and don't know what you are doing. People can converse, even sound articulate, walk, and conduct activities in a blackout. They make choices and rationalize- The most common effect is the loss of memory afterwards, not the loss of honesty and integrity. If a person were unconscious during a blackout, they couldn't do all the things they do: like sit in a bar and pick someone up. They would be flat out cold lying on the pavement, which is end stage of a black out episode.