I have known several men, non gay, that just behaved more like women than men. that was fine, and as far as I know they didn’t swapped gender.
Like you can be a duck, happy when around dogs but still be a duck.
Note, again, I am talking about one specific "type" of gender dysphoria, social dysphoria. There are usually far more facets that come into play as well.
And that's also a way you know you're trans, and not just a man that loves spending time with women. Because the relationships dynamics and social expectations are totally different regardless, we feel out of place. And not being seen in the correct way causes ... pretty deep negative feelings.
To be honest? I ultimately arrived at the fact that I just feel happier when I present femme-ish. Usually still jeans and a t-shirt though--I'm not particularly hyperfeminine, as that's just not who I am.
I've decided that it works better for me, and that's enough for me.
Is it silly to "swap gender"? Absolutely. All notion of gender is silly, in my experience. We're told to perform certain appearances and actions and ideas, to socialize and be around people in a certain way. People treat you wildly differently (trust me, sigh) when they look at you and bin you as a woman versus a man--you wouldn't believe how stark of a difference it was even with old friends the minute they started physically perceiving me as a woman.
All of us are just trying to get through a wildly gendered world in a way that makes us happy--the least we can do is allow people their choice of the role they play in this grand performance, as all of us everywhere are acting.
'Transition' for me was just finally deciding that I got to pick how I socialize, how I act around people, how I dress, and so on. Someone could call me a man, perhaps--I wouldn't particularly be fond of it, and it would probably come across as unusual to others given my appearance, but surely it's a thing that could be said to me.
10 years ago I was one of those who believed it to be a mental illness but with age i start to realize that being judgmental without understanding is often a recipe for disaster. Or maybe that’s my testosterone level dropping that make me soft… who knows.
It took me enormous effort to relate to other men, and I was never sure if I was doing it correctly. I would go out of my way to try to learn "how to man," including having typically male-coded interests (like sports, or home repair) that I really didn't actually care about but knew I had to because it was socially expected of me. I knew I had to, because I had to operate in that world, but I was never comfortable, none of it ever came naturally and all of it just felt wrong.
I was desperate to relate to women. It would hurt that I wouldn't be able to participate in that world even though I longed to be a part of it. Often my wife and I would have grill out parties, and I would be at my expected place outside with the guys, talking stuff I hated, but I longed to be chatting with the other women inside. I feel comfortable as a woman, and much more comfortable relating to other women in my life.
Do I still have male friends? Of course. I have men I worked with for decades and that I'm still friends with. Our relationships definitely changed a bit, but we still have shared experiences that bind us together. At the same time, with my female friends, our relationships definitely changed as well. Things felt different. Our conversations got deeper and more meaningful, and I feel like I "know" some of them better than I ever knew any of my male friends.
I also kept some of my male interests because I'm interested in them.. I still love aviation and trains. Definitely male-coded interests (though there are quite a few more women than one might expect.) I also picked up, or in some cases learned to stop repressing, typically feminine-coded interests. I have far more fun with dress than I ever cared about doing as a guy. Or, now I proudly own that I read romance novels instead of sheepishly hiding my kindle.
[0] https://genderdysphoria.fyi/en/social-dysphoria