If my description would be not clear enough I just leave shorter description of what actual issue is, above reproduction steps and configuration still applies.
If you attempt to login with facebook first it will use facebook email.
If you will login using any other provider, e.g. google or twitter then logout, then use facebook to login, it will create wordpress account using some example email, instead use existing wordpress account that matches facebook email.
The issue occurs ONLY if you will first login to other provider then facebook. The issue does not happen on other login providers.
