I understand what you are saying. I am of the “there is only me” camp too, and don’t have “switches.” But cut the girls a little slack! The English language is a wonderful tool for conveying ideas and emotions.
I sometimes mention “He” – but I’m not talking about another personality – I’m talking about myself and using language as a tool to convey the use of my masculine traits (which we all have), to explain something, usually in a comical way. I suspect a lot of girls use language to put across ideas and feelings, but the words themselves should not be taken literally. “I’ve put him back in his box” is a comical way of expressing a concept and not a statement that I see myself as two separate unintegrated parts, its just a manipulation of the wonderful way words can be used.
Similarly “I feel like a woman when I pull on my panties” – shouldn’t be taken literally – its the expression of an emotion or feeling of pleasure we all feel. It doesn’t imply that I don’t feel like a woman when I am not wearing panties.
I am only talking about the use of language as a tool for exploring our lifestyle, not the deeper meanings about gender identities. I am not disagreeing with you.