We are still seeing the same pop up also. We don't use or have any templates. I had assumed its related to our signature as it occurs only when I change the sender address (From), which triggers a change in signature (we have several email addresses in our outlook profile that we send from)
I now just cancel the pop up when it appears rather than waiting, and everything continues on as it should. So it appears to be superfluous, and would be fantastic if it didn't appear at all. It is not a big thing, but as we are trying to automate and streamline our workflow as much as possible, it is an unnecessary annoyance and mouse click.