This is a misrepresentation (not by the poster but by the author of whatever the poster is quoting). Double majoring does not yield that - that implies a causation. There may in fact be a correlation with double majoring and higher incomes (for people who don’t go to grad/professional school) but there is the obvious confounder that double majoring is difficult and as such the people who do it are more likely to be academically enriched than those who don’t. This would mean that someone who is capable of double majoring but chooses not to would also likely have a higher income. This is analogous to how at Brown University, the classics department has a 100% placement rate for medical school stretching over a decade. Think about what kind of student is a pre-med classics major and ask yourself what accounts for the high success rate - the type of student being discussed or the classics major.
This is coming from a biology/classics double major, d1 varsity athlete, fraternity president, now in MD/PhD program. I only went out 2 nights a week generally though (especially if say you average out over the course of an entire academic year where in the fall and spring I might do 1-3x/week but in winter I would do 0-1x/week - and probably more often 0 than 1). Also does it count if I took the night off from work but stayed in to just hang or play video games with friends so that I could wake up without a hangover and get straight to work?