Just got this response querying diamond challenge & mlife
Went searching and found this thread. Bit disappointing Hyatt don't have a consistent stance on this.
Dear Mr. Arzach:
Thank you for contacting Hyatt Gold Passport; I appreciate the
opportunity to assist you.
Per your request, MGM resort stay do not count towards the 12 nights
required for the Diamond Trail Offer.
Please do not hesitate to contact us if you require any other assistance
with your Hyatt Gold Passport account.
Best Regards,
Hyatt Sales Associate
Global Contact Center