I wrote to my CVP several hours ago and am awaiting an answer. I fully expect to hear the boilerplate answers either that it's on new bookings only or only applicable to certain bookings.
HOWEVER, as I (a retired attorney) wrote in my email to him: I note that the "fine print" of the offer does not contain any exclusionary language restricting this to "new bookings" only, so, by the plain, unambiguous language of the email/terms of the offer, I am entitled to the doubled amount of OBC..."
I can also tell you that I clicked on the "Destinations" link at the bottom of Princess's email and it led me, through a series of multiple screens, to my cruise. Yes, if you click on the buttons higher up in the email, they will bring you only to certain cruises that Princess is calling "deals". But the offer does not appear to be exclusive to just those cruises, as other links on the same email will expand the field of cruises. (And, yes, you better believe I took screen shots of each screen as proof that the link got me to my cruise.)
As to what that CVP posted on her FB page, that may be what Princess intended and
what the promo code may show internally, but the email blasted to all of us does NOT say that anywhere. I would argue that Princess has to abide by the email that it sent to all of us.