Words have power. Using the enemy's terms empowers them by helping them define the narrative. Using the enemy's terms gives them the advantage straight out of the gates.

Transvestite (n.) "person with a strong desire to dress in clothing of the opposite sex," 1922, from German Transvestit (1910), coined from Latin trans "across, beyond" (see trans-) + vestire "to dress, to clothe" (from PIE *wes- (2) "to clothe," extended form of root *eu- "to dress").

As an adjective from 1925. Transvestism is first attested 1928. Also see travesty, which is the same word, older, and passed through French and Italian; it generally has a figurative use in English, but has been used in the literal sense of "wearing of the clothes of the opposite sex" (often as a means of concealment or disguise) at least since 1823, and travestiment "wearing of the dress of the opposite sex" is recorded by 1832. Among the older clinical words for it was Eonism "transvestism, especially of a man" (1913), from Chevalier Charles d'Eon, French adventurer and diplomat (1728-1810) who was anatomically male but later in life lived and dressed as a woman (and claimed to be one).

Dressing to be something other is the same as a clown dresses to appear as a fool or as an actor/actress does to portray a certain character role. Dressing to appear like a girl is not ever changing the biological fact of who they are. So the word gender, from Latin gener- (stem of genus ) which means 'kind'; 'sort' is used erroneously, falsely, and is a lie. We are really talking in terms of 'to dress'.

The question is what is the motivation for them to act like this? I don't think it is difficult to assess and any parent with common sense would be asking this question.