I will forward your question to someone with better knowledge of automated testing approaches for Visual WebGui.
The small tests I made to verify, they agree with your results. When doing CODED UI testing, the capturing occurs on the UI element affected (clicked for instance). The cuid attribute, added by UniqueIdExtender is added on the VWG Html element only, not on the sub elements. This means the cuid will not be detected by the capturing process unless you click on the VWG node, and for a RadioButton for instance, you are most likely to click on either the image or the text, neither of which have a cuid attribute, so the capturer captures screen coordinates, not cuids.
Maybe there is some other approach that needs to be taken and possibly the CODED UI testing does not quite fit Visual WebGui application. If you go back to the thread you referenced here, and take a look at the comment made by KristofBerger, this Ranorex package seems to be able to handle Visual WebGui testing.