“So the extra Chasidish boys can marry the extra Litvish girls.”
Someone who is “extra litvish” would probably be compatible with someone else who is “extra litvish” and not the other extreme. Maybe someone moderately litvish can marry someone moderately chassidish.
Kidding aside, the chassidish girls are comaptible with litvish boys and do marry each other. But darned if you’ll find many litvish girls willing to buy into and marry chassidishe boys.