Kids don't know about college demographics. It's a dumb thing kids say to tease each other. Like 7 year old kids. It just means boys are stupid.

From what I remember, the taunt predates women overtaking men in college completion (which happened in approximately 1995). It's pretty old at this point.

Here's a newspaper article mentioning it from 1993:

https://www.latimes.com/archives/la-xpm-1993-01-31-tm-825-story.html