I'm thinking that's a little harsh when there's a tried and tested escalation point....a support ticket (one comes free with your licence)... Try that with Microsoft without having an EA.
Now that's out of the way, I'm trying to understand why all the steps, some seem unnecessary. We had a similar migration with a few more mailboxes. Some were ActiveSync. We created the mailbox within SM, enabled ActiveSync, used the Migration Tool to transfer any emails from their old mailbox, the user opened Outlook 2013 and created a new profile (entered their email / password, chose Exchange ActiveSync, profile created) then... Went and made a coffee whilst the mail synchronised. We've done this quite a few times now without an issue with SM.
Yes, the client is re-downloading the mail...but far better and automated.