I recently started to see “please enter the email address associated with your user account. your username will be emailed to the email address on file.” in my Analytics of my Joomla 3.x sites.
My first Google search takes me to Akeeba’s site.
My next step is to contact Joomla and Akeeba to see if this is going to be an issue.
I will post more info if I get. I hope this shed some light on this.