That's a very good point.
Sadly within most minority groups there is internalized phobias against their group. You tend to see this quite a bit within the lgbtq+ groups. For example masculine gay men tend to idolized and effeminate gay men shamed.
First off, Being trans isn't just about your genitals. Lol. A trans man is still a man even if he is using his vagina, and a trans woman is still a woman is she has a penis. It's about their mental gender not their physical gender. Many trans people do get gender affirming surgeries but it's not required.
There are trans people who have dysmorphia towards their genitals and often will then aim their hate towards those who use said genitals. So yes, those who discriminate trans people, even if they are trans is a form of internalized transphobia. In this case with the the trans male Being pregnant, some trans men view this as a threat to their masculinity they are trying so hard to prove. Being a pregnant man is something the world doesn't see often and is often ridiculed by the media therefor some trans people view this as a threat to their validity. But what they don't realize is they are just reinforcing the world to not validate us and use us a mock able tagline, when what we should be doing is educating people and letting them Know it's not that big of a deal.
But transphobia takes on many faces. Trans people often are judged within their community based on how passable for a Cis person, as if being trans is soemthing shameful you should hide, therefore giving trans peolle who do pass what is called passing priveledge.
Even though I am Fortunate enough to be considered passable I don't personally hide my trans identity as I personally don't feel trans rights will get any better if we aren't visible.
I hope that kinda answered your question, but this is definately an ongoing topic.