Sure - Coinbase isn’t the blockchain. It’s an exchange, and one operating in the US. So it’s taking measures to implement KYC and perhaps other security protocols, but none of that is required by the Ethereum blockchain or have a wallet.
And I think it’s entirely possible that if they don’t want the hassle of designing a new blockchain, the Fed may forego having an official digital version of the dollar. It’s also possible that given the resources of the federal government and the apparently modest requirements to start up a blockchain, they might choose to do that as well.
What I doubt very much is that the Fed would create an official dollar digital token on an existing blockchain with the characteristics of Ethereum. Existing blockchains tend to regard the “decentralized” leg of the blockchain trilemma as sacrosanct. The Fed, by its nature, will not - so any blockchain that they’re willing to stand behind a true US dollar token is going to place a lot more control in the hands of the Fed (or a highly regulated private entity) rather than the “no one’s in charge” structures out there today.