It has nothing to do with Bitcoin... it's a bearer credential to a server.

Can that server hold custodial bitcoin? Sure, but the server still sees the Bitcoin flows in and out.

It doesn't add privacy to Bitcoin, it's effectively adding privacy to Json-Web-Tokens.

Take note of who's misrepresenting it and who funds them.

The appropriate use of ECash will be much less exciting, like setting up private chats on paid nostr relays.