Thanks for sharing, have the same reversal of first and last name issue between amex and marriott. I know it is late now but can anyone suggest whether waiting for amex name change is better (they said 24 - 48 hrs) or create new bonvoy account and link. Don't have lot of points but that is connect to the HDFC MB card though.for me, Amex seems to be the culprit as they are referring to your "name" that comes in the email once your card gets approved (below format) even though if you have a different first/last name in your card (short name) or in the statement.
I was struggling for 2 weeks between Amex and Marriott and then created a new MB profile where I gave my first name as "xxx" and last name as "abc" as per the card approval email and it was quick instant linking and even tried to transfer 100 pts and it got reflected in 10mins in MB account
Dear xxx abc,
Congratulations! Your application for the American Express Membership Rewards® Credit Card has been approved.
Your new Card should reach you within 3-7 business days.
Also once name change is done, does the linking happen instant sometimes if all is fine since that is also mentioned 48 hrs and that would mean it would cross 15 Dec on worst case
Thanks for your help