Is not the air intake and air cooling elements themselves that are masculine per se, it’s some of the designs for air intake and air cooling elements.

Rule of thumb is that the bigger and more attention grabbing it is, the more masculine it tends to be. Use lots of straight lines and (faux-)chrome elements to grab attention for maximum masculinity. Or just use the hot rod style cheat code and completely break the contours of the car for ultra masculinity.

Simple example would be comparing the front of a VW Golf with the front of a BMW M3.

With the Golf, most people don’t even realize they’re staring at the air intake, whereas with the M3 it’s staring you in the face, some might even call it “aggressive” looking.

Yes, I gather that you didn't talk a lot to design people and marketing people, but 'masculine' features/design exist. Rough, agressive edges will sell well with western males, empty spaces with others, whereas fuller and more round designs will sell well with western females.

That's also why tech companies, following Facebook's lead, redesigned their icons/website to be less marked, a bit more unisex.

It's also why I think that if X don't want to be an incel's nest, will have to redesign sometime soon. Its users are 4% more male than last year (59%), and it was one of the most masculine social network already.

The grilles and other air intake openings definitely got much more aggressive since 2015, it's one trend of car design I hate because it's just there for shock value.