There are reports (1,2) that American Express can now see across accounts if you have multiple logins. Reddit user Slytherin23 first reported that they no longer see upgrade offers for the Amex gold as the login with the gold card knows the user has a Platinum on another login.
Reddit user Parts_Unknown- then confirmed this was true, even if the MR accounts are separated. Their P2 shows ‘add an AU’ offer for their Business Platinum card when they are browsing cards on their other login with a different membership rewards account.
