UWP is hardly consistent. Just as a quick example, the context menu in the start menu is slightly different from the context menu for the task bar, which are both very different from the context menu(s!) which appear in the Windows Mail app. Or how the context menu in the start menu can exit the bounds of the start menu, but most popups/menus in UWP apps are fully bound to their parents.

Yes Windows framework #935 has actually turned out to be pretty good.