I don't even know why an email address is required to join a bounty campaign!
I don't see how it can be used to detect cheaters, creating a new email is totally free and won't take more than 2 minutes.
"Email addresses will be hidden, and won't be used for any spam / promotional actions. Emails are to verify users when comparing data with projects own data."
can you, please, add the link of the topic from where this sentence was taken.
Probably, it's an innocent mistake and he just forgot to remove or hide the emails' column. Contact him and let him know about it.