The noun ‘feminile’ is masculine😱

This is the English version of ‘femminileが男性なんだけど’.

The question began when I searched the difference between ‘il mattino’ and ‘ la mattina’. Then I found I was in a labyrinth myself.
I found a very strange sentence in Treccani.

　il femminile mattina è leggermente più diffuso.

? il feminile?

I wondered if the Treccani sometimes makes mistake.
But that was not true. It was the correct sentence.

The dictionary says that ‘ feminile ‘ used as a noun is a masculine noun .

BUUUUUT I’m not convinced.

PHOTO : Antipasto a Rocanda di Riz Carlton Kyoto