It seems that we MUST use a licensed mailbox for Workflow to link to Office 365 to create Exchange items. Is this correct?

After struggling with this for a long time with multiple clients it seems that even if i create an O365 user that has Exchange impersonation rights and CAN successfully pass the Microsoft Remote Connectivity Analyzer test, that Autodiscover will fail if the impersonation user doesn't have a valid Exchange mailbox. If I force the Analyzer to not do Autodiscover it works, but then Workflow fails with an Autodiscover error.

(The error with Autodiscover says that it can't find a mailbox, which the impersonation user does not have.)

Must Workflow pass an Autodiscover test when using these activities for Exchange integration? If I provide the full EWS path why would it care? Is there a way to force Workflow to bypass Autodiscover? If not, then it seems that in O365 we would have to provide a fully licensed mailbox just to do Exchange integration.