Same issue here. The wrong email address is displayed in the "From" field, even though it is sent from the correct (default) one. Only the very first time after opening Outlook anew, the "From" field displays the correct (default) email address.
While the feature itself works, this is clearly a bug; a very confusing one I have to say, because the user cannot be entirely sure from which email address the message is sent.
I hope that this issue will get resolved in a future update, because this feature is the only reason why I purchased this software an hour ago.