I think strictly isn't accurate at all. I'm a
Kristina "
Kris" born in the 80s. Actually, I have plenty of nn but I prefer
Kris.
I think in my experience,
Christopher and
Christian were so popular, along with
Christina and
Kristina, that the girls in my school, me included, just tried to find a name that no one else was using. And the boys had
Chris covered. So
Tina,
Christa, Krissy,
Christie, etc. were popular.
I'm not so sure how much the generation today likes masculine nn on girls. Most who like more masculine names will probably choose a boy's name or surname over a feminine name with a masculine nn. Just a thought.