Everything MisStarrlight said is the way it works at my counter too, but I didn't have a formal interview, just a private chat with my manager about why i want to be product specialist and what i think i can bring to that role.
Not sure about the rest of the world but in Australia the Product Specialist role is now 12 months and there is a lot more responsibility to the role.
I got the role 2 weeks ago, yay!