Users are only provided with a link to the email setting form once, when it's not set, and have no way of changing their email unless they navigate to the page directly.

If OAuth isn't able to find the user's email they are prompted to enter one manually, but can still check a box saying their email should be automatically updated, and aren't allowed to not enter one manually. That makes sense because we couldn't find their email from WP, but makes little sense to the user who has no idea we failed to get it automatically the first time. The change email form shouldn't allow users to both enter an email and check the box. It should be either-or to reduce confusion.

If a user has selected use_wp_email but have no email set (i.e. oauth couldn't find their email or they need to re-log), the no-email message should provide better context for this.