There's a difference between "parts of people don't give birth" and "a person being born is wiped out of existence just because it doesn't suit our reporting window". If we would report every month, we would still have 0 people after a million years.

I don't think using regex on a kata called "Regex validate [...]" is missing the point. This regex is also O(n) with respect to the input length, not O(1).