For me it's not the 'two dads/two mums things' as that exists anyway with same-sex couples. Unless one of these types of existing familes eg, two dads who are gay tell the child a lie that one of them birthed the child, no problem, as, just when children are adopted etc, there are age-appropriate ways of telling them about a) how babies are made in general b) how they joined/are part of whatever type of family they are in.
The concerning thing is, whichever way this is explained to the child as they grow up, in whatever age-appropriate ways, it is likely to be telling them something that is a fiction, and outside reality, particularly if the story is 'your dad is a man, and he was pregnant with you and gave birth to you'.
And to take it further, in terms of genetic illnesses etc, in the future, if the child is female and has been fully inducted into believing they have a 'father' not a mother - how does the conversation go that's common in the GP surgery...is there any history of xyz medical conversation in the female side of your family history....?