Actually, I don't think there's a good argument to add either U+1FAC3 PREGNANT MAN or U+1FAC4 PREGNANT PERSON: expressing gender can already be done with a modifier like how skin/hair color and professions are also expressed, and we already have U+1F930 PREGNANT WOMAN.

For example, this is the unicode sequence for bearded lady:

  U+1F9D4  person with beard
  U+200D   zero width joiner
  U+2640   female sign 

So a pregnant man could simply be this expression:

  U+1F930  pregnant person (woman is implied by lack of modifier)
  U+200D   zero width joiner
  U+2642   male sign 

But no, instead we must have this combinatorial explosion of compositions because Unicode can't decide if it wants to be a symbol library or an expression library. So now, we have duplicates like U+1F40F ram and U+1F411 ewe, U+1F404 cow and U+1F402 bull, U+1F9D2 child and U+1F466 boy and U+1F467 girl (but a baby boy must be expressed as U+1F476 U+200D U+2642), U+1F468 man and U+1F469 woman and U+1F9D1 person, and U+1F385 Santa Claus and U+1F936 Mrs Claus but also U+1F9D1 U+200D U+1F384 non-gendered Claus.

The concept of notability is similarly subjective, the issues like the mentioned race/gender identity (or e.g. the Russian-Ukrainian war recently) are perceived as very notable on English Wikipedia.