this is a typical meta/facebook/instagram sign-up and log-in UI from the web.

and since dev.meta.ai supports meta account sign-up and log-in for individual users, you'd see this. As for the other accounts, has anyone else used this same browser or laptop before (e.g. shared device), so it must have cached previous sessions or accounts used from the same device.

try to clear the browser cache and session cookies. and it should be gone.