Yes, I know that the values that you get from glazing manufacturers are almost always U-factors and NOT U-values. U-Values and R-Values are typically only used to describe opaque constructions.
Also, the recommended way to use the SimpleGlazing material is to plug the “Whole System” U-Factor rather than the “Center of Glass” U-Factor. While it’s true that different window geometries have different amounts of frame and therefore should technically have different constructions, this tends to be at a level of detail that’s beyond what is needed to get decent estimates of energy use. That is, unless you have very different types of framing materials across your windows or you have very different types of window frame geometries.
In the future, we will add detailed frame objects to honeybee-energy WindowConstructions, which will make it easier to just specify the frame material and EnergyPlus will take care of computing the effect of the frame for the different window geometries: