In real life, a tomboy is a young girl who likes young boy things. That’s all there is to it. The label is really quite shallow and has no philosophical implications. A woman identifying as a “tomboy” past high school age is kind of ridiculous, like a grown man identifying as class clown or spelling bee champ.
The “tomboy” discussed on the internet is just some meme fetish archetype with little relation to reality. Your femboy tomboy moth girl dommy mommy gf will never exist, so quit dwelling on it.
I tend to be slightly put off by non-past self-identification as a tomboy, mainly because I'm not used to it employed that way. Even more, even if the tendency associated with the term is pointed out, I still hardly hear the term-- much less as self-identification.
However, I was (and still am) all but convinced that it would be helpful to deduce a definition of a tomboy that was as modular as possible, in part because-- as it came up in this thread-- "what young boys like" has layers of variance depending on culture, and having some interests that may be seen as principally in a boy's domain (e.g. sports) wouldn't readily lead to one thinking of someone else, "what a boy-girl". There's certainly a "spirit" associated with the archetype that transcends the interests themselves; even if you wanted to say it was a mere matter of interests, what one takes to isn't something that occurs in a vacuum.
In fact, because of this thread and some related conversations, I currently figure that what people recognize as "tomboyish" is the quasi-masculine spirit resultant from a girl willingly pursuing interests with no regard to-- and sometimes in opposition-- to their naturally associated sex-based norms and obligations (whereas women
tend to conform to such things), and the reality of there only being two sexes means that these interests are almost certainly male.
Speaking of spirit, I mostly agree with the spirit of your latter statement. Rather than an appreciation for a certain kind of woman, what ends up (often) discussed on the internet is a collection of symbols and patterns to which many of these people have conditioned themselves to be aroused upon their identification. There's also an element of escapism: they consider tomboys much more relatable than other kinds of women because they figure their boyish airs mean that they're bound to be much more relatable. And there's some truth to it, but outside of the occasionally associated fantasy of making them glad to have been born a woman, they neglect the reality that-- in the ideal case-- they can only expect
less of what they fear/resent in a typical woman because tomboys are still fundamentally women.