This came up during Office hours in August. After that I made the posts above and brought it up again during Office hours in September and the answer I got was @Martti: What you are seeing is the expected behavior. If you go look at the legend again, you'll see that there is a small green progress bar towards the top of the 'Progress Through Bar' icon. The forward looking arrows inside the blue bar is what indicates that this task is part of the Critical Path. After digesting and studying the images for a while I can say
Yes with magnification I can see that I know what I am looking for the small green progress bar towards the top and the little white space under it after the act thru date.
So it is as designed. What was confusing to me was that what the legend displays for the critical is inside the bar as the bar is not displayed and that the bar where the legend has the progress displayed is also critical. Separating them would be ie. having a critical bar without the progress and a bar with progress without critical would be more clear.
This is another item in addition to the milestone baseline symbol that could be improved. As I wrote above the graphics in the documentation could also be clearer. The forward looking arrows could be black in the chart, the legend and the document, but now they are only a somewhat darker shade.
All critical tasks
For Comparison in OWB