I believe this is just the default name of the profile when you you don't log in on Chromium, you can see it in the code in dice_web_signin_interception_bubble_view_browsertest.cc,
primary_account.account_id = CoreAccountId::FromGaiaId("primary_ID");
primary_account.given_name = "Tessa";
primary_account.full_name = "Tessa Tester";
primary_account.email = "tessa.tester@primary.com";
primary_account.hosted_domain =
is_primary_account_managed ? "primary.com" : kNoHostedDomainFound;
However it seems like a poor idea to tell you that you're "already signed in" to an account that you never signed in to, and don't recognize.
Tessa is already signed in to this Chrome profile. This will create a new Chrome profile for sam.sample@intercepted.com– squillman Aug 29 '23 at 20:42