I just did a 2BM for a Amex Plat and Gold.
I got an RSVP for the Gold, and when I entered it online they also gave me a link to the Platinum
I signed up for both, once I got the cards, the system wasn't linking them to have them both on the same login ... I called, and the rep told me that the issue was the Gold card didnt have the SS and DOB on file, I gave it and then they were able to link them