Land of the Subtle...Filled Regions in Revit 2019

A colleague of mine recently pointed out a subtle change to the filled region settings in Revit 2019.
I have been so distracted by the new (and very cool) background / foreground options in Revit 2019 that I didn't notice in the filled regions dialog Autodesk have made a subtle change to the terminology & method to making a filled region transparent or opaque...