This is exactly what we’re talking about when we say trans activism reinforces sexism. To say that lesbians or any gnc women are really male is pure misogyny. Women are not defined by heterosexuality or by femininity; to believe that we are is completely backwards sexist thinking.
It’s also pure homophobia. We’re back to archaic thinking such as: heterosexual is the only correct orientation so homosexuals must have been born the wrong sex and bisexuals are mystically both sexes in some way.