This is very interesting. I don't know how I've never seen this mentioned before. Technically, the previous paragraph explicitly denies that this is allowed
A maximum of 15 Elite Night credits will be awarded per Marriott Bonvoy program member account even if the member has more than one Credit Card linked to their Marriott Bonvoy account.
FWIW I have the Bonvoy Business and Bonvoy Brilliant from AMEX and I only got 15 EQN. However, I went to the current T&Cs for the AMEX cards and both do indeed have the exact language you posted here
Marriott Bonvoy Lurker can you elaborate on this huge contradiction in the T&Cs?