American Airlines elite members would receive select on-property benefits while staying at Hyatt affiliated hotels and vice versa. If you had elite status with both, you could also earn World of Hyatt points for American Airlines flights and bonus AAdvantage miles for Hyatt stays.
You can access the partnership page here.
American Airlines Concierge Key members were given World of Hyatt Globalist status while WoH members could fast track to various tiers with AA.
Now, however, World of Hyatt concierges are contacting select Globalists, offering them Executive Platinum status through January 2021.
Executive Platinum status with AA is worthwhile and comes with Emerald benefits when flying other Oneworld airlines.
It always makes sense to sign up for these partnership offers even if you don’t plan to use them. They will inevitably lead to additional bonus points and miles opportunities or even a top tier status, as is the case here.
I dropped an email to my Globalist agent at the Hyatt to find out if he forgot to call me or if he is still in the process of distributing his lot (they are calling not emailing members). He may have had trouble getting through as none of the programs have a live phone number of file for me (I use Google Voice for loyalty programs).