I've looked and can't find an answer, though I'm not real sure what to search for.
I have:
2 Business Platinum cards
1 Schwab Personal Platinum card
From what I can tell, AMEX must aggregate spending cross all platinum cards. I say this b/c I used the Schwab card to access the Cent lounge recently and my 2022 spending on that card was only $10k. My spending on one of my business plats, which is tied to the same online ID as the Schwab card, was only $26k. My second business plat, tied to its own online ID (though I get that likely doesn't matter) had $700k+ on it.
I received three emails identifying each of the three cards stating that I have access to the lounge w/ free guests (up to the limit).
So it's pretty clear they are aggregating spend, my only question is if they are aggregating only across plat cards (non-cobranded) or all cards tied to a TIN. Any thoughts?