This sounds wrong. Since Matrix is federated, you can still be echelon, just not @echelon:theserveryoutried.com. Furthermore, this is just the MXID, the Matrix

This sounds wrong. Since Matrix is federated, you can still be echelon, just not @echelon:theserveryoutried.com. Furthermore, this is just the MXID, the Matrix ID. This is usually de-emphasized in the UI and only used to disambiguate and add users (as you say). What is usually displayed to users are display names and these are allowed to have collisions, in which case they get disambiguated via MXIDs.