If a way of signing in presented a verified email address matching an existing SIMCOAI account, it used to be attached to that account straight away, with no confirmation. That is fixed: linking now only happens when you start it yourself, signed in as the account you want to add it to.
There's a new Connected accounts tab on the Security page for this. It shows which providers can sign you in today, lets you add another one, and lets you remove one — you always keep at least one way in, so the last one can't be disconnected by mistake. Adding or removing a connected account asks you to re-confirm your password or two-step method first, the same as every other change on that page.