Edit: The key is that USD cannot be both digital and private at the same time.
I hear you, but by your rules *nothing* can be digital and private at the same time, because simply by moving through a 'trusted third party' privacy is broken.
I am arguing that the digital dollar is "private for all intents and purposes" with a disclaimer that nothing that isn't decentralized can ever truly be private, because it must pass through a trusted third party who can spy on you if they like.
But for most of the population they are used to thinking of their dollars as private, and in some respects they are more private than bitcoin which has a totally public ledger. But as I said, I agree that digital dollars are never truly private (nor is any asset stored by a trusted third party).
I think the comparison holds as long as you make that very clear.
Fungibility rather than privacy is the more critical issue here, unless the trusted third party creates a bearer and digital USD instrument. This however will likely run afoul of AML/KNC laws and regulations, so most digital USD instruments are not fungible and by my strict definition not private. Monero on the other hand is digital, private, fungible and legal!
I know some would say that bitUSD would qualify digital, private, fungible and legal but bitUSD is dependent on the BTS/USD rate staying above a certain threshold for the peg to hold.