I have thought about this a bit.. here is IMO a pretty insightful quote into personality
"When I say that Professor Lindzey’s left shoe is an “introvert,” everyone looks at his shoe as if it were something the shoe was responsible for. . . . Don’t look at that shoe! Look at me; I’m the one who is responsible for the statement."
The mere existence of the word feminine implies there is a dichotomy between male & female worth observing. When we search for this difference, we find it (funny how our brains are good at finding whatever they search for..). That confirmation leads us to form the perspective "women & men are different" and now see the world through this construct. From then on, confirmation bias is enough to sustain the correctness of this concept.
When a person who has no idea what feminine means, behaves in a "feminine" manner, others call them feminine (because this concept is near universal). That reinforces the concept, and like a virus the concept spreads to yet another person.
So the more existence of femininity as a cultural construct in a sense makes it all the more real. It is partly a "social reality" [1].'
Its like in cultures where the language has 1 word for 2 colors (from perspective of english speaker), they have observed that these people literally perceive less difference in the colors... so is the difference between blue/green a social construct or reality? The lines between social construct & reality are very blurry :p
[1] From Sapiens - Yuval Harari