I traded messages with a Plex employee regarding the notification e-mails.
The e-mails regarding the security incident (announcement) are still going out.
The messages for accounts using a password vs SSO login are worded differently, as different action is required based on the login method.
If you’ve multiple Plex accounts, then you will receive multiple e-mails.
Check the TO: address in the e-mail to see which account received which e-mail.
Each e-mail address should receive only one notice, but it isn’t 100% impossible that a second might be received.