The feelings/emotions/sensations are legit and are a complex mix of nature and nurture that you can’t really change voluntarily. They exist in the body and mind.

The grouping of those feelings into a rather large container-terms that also includes social roles, looks, expressions and a host of other stuff IS a social construct.

Like, a gemstone can be red, triangular and opaque, and those are objective properties. But calling it pretty is a social thing. The big difference is that “this is red” is a whole lot simpler to put into words than anything gender related.