Originally Posted by The Viking
But: Be aware that both these codes require that you pay with an Amex cc, and you will probably not be given the extra privileges like upgrades, late check-out, amenities etc. unless the cc is Centurion or Plat.
The rules only require that you pay with an AMEX product; the rules do not indicate that you have to pay with the Centurion or Platinum card. However, as others have pointed out, the rules also explicitly state that you have to book through AMEX.