It's (fortunately) not correct.

It's a contract between the partner bank and Amex. The bank must settle the monthly statement also, and the pre-approved standard amount is higher for Centurion than for other Amex cards.

The bank has to ensure that the customer's deposits are high enough to cover the shadow limit. The shadow limit will be increased later by analysing the actual expenses, if it's a new customer.

In all cases, expenses "higher than usual" may result in a call to the bank before approval.

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Note that in the last years, Amex launched many cards (with the classic design) together with partner banks (Santander Bank in Spain, for example). These cards are not co-branded cards in the common sense like HHonors or SPG cards. The partner bank is responsible for acquiring and servicing the cardmembers, but must enforce the criteria set by Amex.

The International Dollar Card is marketed directly by Amex Europe (UK) or by partner banks.