Are the first 8 digits of a pnr always unique?

Hi -
After reading the documentation that is sent along with the appointments bulk data, especially section 4.5, I have a question.

I seem to understand that:

  1. the entity “person” in CH is composed with a name and a URA.
  2. a “person” is given a pnr of the type 123456780000
  3. As of 2009, URAs are not public, but CH does receive notifications of changes to both names and URAs for a specific appointment.
  4. When changes to either name or URA (actual new values in URA are not public) happen, the last 4 figures of the pnr increment.

My question is then the following: it seems to me that to get the unique ID for a person, I need to get the first 8 digits of the pnr.

Is this correct? Or is there any unintended consequence in this approach?

Thanks a lot!