Responding from the other side of the divide (if it is, which I don't know). I started out with a nickname that was my initials. And now have a name that is similar to my given name. I even hear it that way sometimes which is nice. Each time I did that it was empowering. I wasn't sure I was doing any transitioning when I changed my name the first time around.
I know someone who changed his name from Christine to Christopher and kept his nickname. I think it's probably common.
BTW, I once asked my mom if I had been born a boy (sic) what name she would have given me. I would love to be able to know the context of this conversation, but I have found out it is very common in trans people. And she said John. I don't like the name but I am putting a variant of it in my legal name.
--Jay