How does your profile look? Scores, derogs, other cards/limits, any BK? It may be that you qualify but aren’t yet on the Amex SP radar. Sometimes you just have to go for it and see what happens. Amex cobranded cards have more lenient underwriting than their core cards, and it’s said that in the core cards, the charge cards are easier to get than the revolvers. It may be worth a cold-app if your profile is strong enough. Back in November there were several of us who cold-apped for their Delta Gold and/or Hilton Honors cards and got in with scores not typically thought of as being Amex-worthy, in the 640 range. Strength of profile is big with them and once you’re in, your existing relationship and history with them makes a big difference.
EDIT: after I posted, I saw you have the Gold. At this point they do know you and your profile, so it’s likely that waiting for a preapproval is best.