Data point:

I canceled a United award flight (with miles redeposit), and paid the $25 service fee as a Premier Gold member. The $25 cancellation fee was charged to my Amex PRG, but the fee was not automatically reimbursed.

The first couple chats with Amex confirmed that the fee will be automatically post between 2-4 weeks, and that Amex agents can manually post only after the 14-day mark.

After 14 days with no reimbursement, I chatted with Amex again. The agent was able to post the $25 reimbursement manually. Though, I had to explain (very briefly) what that charge was for, i.e. award flight cancellation fee.