Let's first difference the 2 things.
Appealing black men's and serving are majoritarly Fantasy, kinks, arousal factors.
Transitioning in itself is a very profound decision, and it results in most cases from the intimate feeling of being born in the wrong body.
Porn can have that way of influencing your (in general) vision of something, example with chastity porn where you more and more think that it's something natural and mandatory, when a few years before you wanted to put your dick in every hole. That's the effect porn have.
Now of course, if you've ingested Dozens of Terras of Trans blacked porn and sissy feminization surgery porn, you could think they're related, but in my very own opinion, it is not at all.
Transitioning is something you feel inside of you, you feel you're not like you should be, you think about it and reflect on yourself every single second of your life until it becomes more and more clear to you what to do with yourself. It's really hard and demanding mentally, it's exhausting and really a terrible thing to experience.
I honestly wouldn't wish my worse enemy to have those thoughts, because it is just permanent depression and social humiliation and hate. Only because you feel alone and bad.
Yes, in time like those, some turns to smoke, some to drugs and some to porn. In these dark times of someone's mind, porn can have a heavier affect because of 2 things : how vulnerable you are, and how accepting porn is.
In pornography you can be anything you want to be, same as videogames for examples. (That's why so many smelly WoW players plays Elves women and why Bayonetta was created) (or catwoman)
Porn let's you be yourself. And helps you to feed others people your vision of what sex should be. For us here, it's BNWO.
But for most Trans fem, it will stay a fantasy, because it's porn, and porn is a mean to evade from life.
You can see Transitioning as a trip around the world, and the BNWO is a country somewhere, a stop before heading forward.
Some people will just stay here because they love it and want to do more in that stop, but also some people will just visit the touristic places and go ahead on the trip.
Transition is deeper than what you except.
And pleasing men doesn't even count's in the process of your feelings of yourself.
You are you before anything else, and that's the most hard thing to decipher alone.
Who are you ?
And porn has nothing to do with the answer.
PS : sorry if the answer is a little strict and heated, it's just that it's a personal matter and I'm not very good to express myself on serious matters. I mean everything I said, but never wanted to be rude. Just 100% honest.
Peace