What I get from that guide is that we don't need to worry about this email situation and remove email notifications and ask users to opt-in again like people who run Mail chimp lists need to (if they didn't have double opt-in turned on previously). We just need the options to be available to opt-out, and for us to help them opt-out if they ask us (admins). It's not specifically clear though, so I will ask the question wherever is appropriate in relation to that guide in a moment.