It might help to understand our history of Age of Consent laws.
1st one appeared in the 12th century (England at age 12), which was connected to the start of menstruation.
It wasn't until the 19th century that litigation moved it to 16(England again), and basing it off of physiology rather than biological milestones.
There's also an age exception range for underage kids dating (here it's 2 years). That avoid allot of kids going to jail soon as they reach the age of consent after dating anyone a day younger than them.
Nowadays highest age of consent is 21 (Bahrain) and lowest is 12 (Japan).
Sources: https://chnm.gmu.edu/cyh/case-studies/230
https://en.wikipedia.org/wiki/Ages_of_consent_in_North_America

So even if Remnant has age of consent laws, Ruby is likely already of age. And if their age of consent is older than Ruby, Juane is within age range to be excepted from said law.

But I do like what you're getting at. Human population in constant danger, it does feel likely that society would push harder for procreation. Puts a new light on allot of what Ozpin says & does.