Conversations from today.
I guess to answer that question it would help to understand what USD is. It's a promise note from your local government. The government is allowed to select who can hold or create these promises on their behalf. Banks spend millions of dollars for a charter that grants them this special privilege.
Anything outside of these special groups can't really be considered dollars, or maybe a better analogy they would be a promise of a promise. Stable coins are a promise of a promise, as is any other dollar backed instrument like a stock or gold claim.
You can trade a promise of a promise over bitcoin, nostr, Tron, ETH, pretty much anything since it's not actually anything physical.
Bitcoin isn't a promise, it's physical data that you own without a promise from anyone else.
Ecash represents a promise of bitcoin, not a promise of a promise like dollars or any other dollar L2 mechanism. So while it is a layer above the real thing, it's the closet thing to Bitcoin that exists besides bitcoin.