Just because it isn't connected to a bank account as you understand bank accounts to be, doesn't mean it isn't connected to a bank account as banks understand them to be, and you're not entitled to request a statement.
Just because one is entitled to a bank statement as you understand this entitlement to exist, does not mean that the card issuer is obliged or interested in providing one within weeks or even months of the request, especially with the exact format that Amazon or another third party has decided to accept.
Ah I see, so you did realize that the bank responsible for your card would send you a statement, but they wouldn't send it in either the correct format, or within the necessary timeframe. Well that just sounds like a crappy situation all-around.