>>how does a decentralized coin implement KYC for a wallet-to-wallet transfer like you mention?
>the KYC comes during off ramps back to the fiat system
And here we have your answer. It doesn't. In fact using your own logic, I could argue Tornado Cash is KYC'd 'because at offramp' which of course is absurd.
Now that you've made it crystal clear your use case does not include dai implementing KYC, I return to my thesis: DAI is imminently dead by .gov pulling a Tornado Cash on all the underlying centralized collateral locked up in DAI.
I hope you're right, but we seem to be sliding further into the dystopia, not out of it. Notice as time marches on the shrinking number of 'blacklist' FATF countries and the end of non-KYC/AML finance world-wide. IMO dai will go the way of bearer bonds and shares. The fact that all that underlying capital is in real-world bonds/paper/notes means cooperative financial task forces have these stablecoins by the balls and soon they will start squeezing.
the exchange i use has already KYC'ed me intensively and they know which wallets i use.