no, unless you get a mail informing you otherwise, that is still your primary identifier. Later signups with murena.io have the murena-id on that instead. Things might change with SSO, but I’m sure there’ll be a infomail on it then.
I’ve left my @e.email login details but changed my account settings to @murena.io because @e.email was not recognised when submitting proof of NCD on Car Insurance because my lowest quote was with a company that deals with everything online.