The key is in the word 'trans' if he's a man who wants to be considered trans doesn't there need to be some kind of transition involved there somewhere?
You would think, but at this point "trans" just means "not cis", in the same way that "queer" means "not straight".
Where regardless of formal definition, by actual usage "cis" and "straight" seem to effectively mean "boring and privileged, like other people".
So saying you're "trans" or "queer" means "I'm more interesting and oppressed than you".
"Trans" was originally short for "transsexual" which did at least have some meaning - someone who was in some way, often hormonally or surgically, imitating the other sex.
But having become "transgender", you have the problem that "gender" itself has become meaningless. If "treegender" is a thing, then how do you transition to that? But it still makes you "transgender".
And who's to say that someone who is "treegender" has to use funny pronouns or dress differently? This MP hasn't said what his gender is, so maybe it's treegender. And he's a he/him masc-presenting treegender man.
Still trans.