So I'm going to submit for that name change as a legacy player but I am confused only about one thing...

They say that you cannot choose the same name (obviously this makes sense in more ways than one).

What I am wondering is which name is the "base" for which decides if it's the "same" name or not? For example, would I be able to change only my last name or only my first name?

Does "same name" only refer to if both halves of the name are identical?

Some clarity on this would be nice because I only want to edit one half of the name but if it forces me to change both I'd rather not apply for it.