I noticed that too.
Hey @The Real timschochet, here is a useful mnemonic device I use to keep it straight, I probably learned it here. You will hate it, but it works. Ready? Replace "transgender" with "pretend."
Thus a "transgender boy" is a "pretend boy" meaning a biological girl. And vice versa. So as TNG pointed out, you wanted to use the "pretend girl" (transgender girl) phrase. HTH.