Those could have been inferred from the main game. You're a courier, so it stands to reason someone hired you. You were shot which implies someone wanted you dead. Beyond that the early history of The Courier is pretty blank. You get maybe, three optional lines that I can think of (Montana impregnation, New Reno clubs, visiting Utah). Even so, all those things don't derail RPs too much. A hometown and more detail can.
No, you were shot because someone wanted your package. You were set up with that specific package BECAUSE someone else wanted you dead.
Johnson Nash told us we were set up.
Christine told us Ulysses was looking for us.
Ulysses says we know the way to the Divide.
And yet, almost one year later, people are incredibly shocked the Courier isn't a blank slate.
Also, I don't see the big deal. The Courier apparently did something bad enough that another person wants him dead, and
that doesn't bother anyone? But omg, he was born somewhere. How dare that [censored] Courier. He should be like the Lone Wanderer and the Vault Dweller and the Chosen One and not have a specific birthpla- oh wait....
I mean look at OP's complaint. "My FO3 character is my FONV one and now it won't make sense." It wouldn't make sense for your FO2 character to be your FO3 one either, or your FO1 character to be your FO2 character. None of those make sense, so why flip a [censored] over the Courier having a birthplace, JUST LIKE EVERYONE ELSE?
Besides, we don't even know if that's the case. "Hometown hero" is super vague and can be interpreted various ways.