Look up proposal L2/20-190. They provide a number of good reasons for pregnant man. To summarize:

- It avoids gender stereotyping of men in Parenthood.

- couples say "we are pregnant". The term pregnant is culturally used for men too as their search shows.

- the emoji is not just for pregnancy, it is also for feeling bloated, full, and hungry.

I sometimes used this emoji for saying that I'm expecting something. My partner didn't like it.