This seems to be the key to the ruling:
93. It is clear that there are two main currents coursing through the Applicant’s life: his clear and settled identification as male, in which sex I find there is abundant evidence that he continues to live; and his desire to have a family. In my judgement, there is nothing further he could do to reconcile these two powerful instincts. To require him to abandon either one for the other would be to dismantle and fracture the person he is. The GRA 2004 and the case law which preceded it recoiled from compelling such an invidious choice.
I find the language very un-legalistic: a 'desire to have a family' is not the same as 'becoming pregnant'. For males, as the judge fully accepts the applicant is, the 'desire to have a family' means forming a relationship with a member of that half of the human race which has the capacity to become pregnant.
It does not mean becoming pregnant himself.
there is nothing further he could do to reconcile these two powerful instincts
He [I'm using the ruling's pronouns for convenience but also because it highlights the issue of what constitutes 'living as a man' ] could have done any one of a number of things any man who wants to have a family can do: he could form a relationship with a biological woman and they could have a child; he could form a relationship with a biological woman who already has children; he could adopt a child; he could foster a child; he could engage a surrogate mother [the Applicant considered this but it was too complicated and expensive..]
[I'm not stating approval of any of these, just pointing out the avenues that are available to men who desire to have a family, as an alternative to becoming pregnant themselves.]
A transman also has the possibility of acknowledging that by deciding to renounce being a woman, he has also, logically, renounced becoming pregnant and giving birth.
The language in this part of the ruling is surprisingly emotive, becoming pregnant is presented as an irresistible biological imperative that must not be denied or it will 'dismantle and fracture the person he is' .
'currents coursing through the Applicant's life', desire to have a family', 'powerful instincts', 'abandoning', 'dismantling', 'fracturing', 'recoiling from an invidious choice'... as prose goes, it's all a bit purple, isn't it? with hints of biological essentialism.