Other than the futanari issue, I would add that at least some of these terms carry some degree of deregatory connotation in either Japanese or English, such as okama. There's a lot of misunderstanding and misinformation about tag definitions among western artists on Pixiv. They are actually シーメール (shemale) or ニューハーフ (newhalf) instead. In such cases, I think it's a matter of the artist not understanding the true definition of ふたなり. If your source for saying futanari sometimes have no vagina is Pixiv, I've seen many such 'futanari' images with only a penis, but they are drawn overwhelmingly by American and other western artists. Personally, I believe a futanari _must_ have both vagina and penis, especially given the origin of the word ('futa' from 二つ, 'na' presumably as the adjective particle, and 'ri' as in 一人 = 'two in one person'). This is a topic I know well, since I find it interesting (I especially love 男の娘) and also applicable to my own personal life as a non-binary person.
