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.