Internet Explorer 11 does not add the Origin header on a CORS request?

Question

My issue depends on a couple of assumptions I hold true.

Assumption nr 1: The Origin Header

The Origin header is required by the browser to be

Answer 1

I just happened to stumble across a reported bug over at a Microsoft associated site that clearly describes my issue. Microsoft staff quickly concluded that:

There is insufficient information to reproduce the behavior you are observing.

Since their first comment and their first attempt (?), they have actually managed to run two different web servers on different ports and reproduced the problem. Latest comment from Microsoft says that they "consider targetting a fix in the future".