I’m not forgetting it, I just think the effect is probably negligible. Even if we assume that the 19 year olds who are left over are the “financially challenged” ones (which I actually don’t think is true for the most part), by the time they’re 21, they should have money put away, plus more earning power, giving them an advantage over the 19 year old who is in the same position as she was.
You are also just finding another contributing factor to age gap. Would you agree that if the standard age for boys became 21, the problem would mostly be solved?