Dictionary definitions are not exhaustive. Otherwise, we couldn’t say that women who had double mastectomies are flat-chested (though to be fair, calling them that wouldn’t be a good idea).
The breast tags are meant to be a continuum. Completely flat is flat chest, the smallest discernible breasts are small breasts, and so on. The character has discernible breasts, and since small breasts imply breasts, which should not be used with flat chest on the same character, flat chest does not apply to her in this post.
Dictionary definitions are not exhaustive. Otherwise, we couldn’t say that women who had double mastectomies are flat-chested (though to be fair, calling them that wouldn’t be a good idea).
The breast tags are meant to be a continuum. Completely flat is flat chest, the smallest discernible breasts are small breasts, and so on. The character has discernible breasts, and since small breasts imply breasts, which should not be used with flat chest on the same character, flat chest does not apply to her in this post.
Also, what would count as smaller than normal? Like, even the implications of something is normal would mean that others are abnormal. Something can be the norm. But even that would be hard to determine as different cultures view it differently of what is considered the norm. And is subjective.
And it seems man use it wrong then. As they apply, the common usage of that term. Which also highlights the problem of using a different definition as the norm.