I believe your team make it purposely as, we could just set different Pattern to make the Combo display differently.
However, this is what I got from my users, they intuitively think the they could just highlight and edit the displayed result in the combo. It sounds perfectly reasonable even to me when I tried the combo for the first time.
This takes me a week or two to explain the way it work to the users only resulting in questions of "why".
It will be perfect if your team could add the "highlight-and-edit" function.