Styling the current page is only possible when using a WP Menu. Then the li-element gets the class current and therefore can be styled. When using Nav Links and Drop Downs the class current does not get applied so the styling has no effect.
In this screenshot you see first the li-element that is a result of a Nav Link. After that you see a li-element that comes from a WP Menu. Both have the exact same url but only the WP Menu one gets the class current.
I’m sure this must just be a glitch that will be fixed in the next version, because the li should get the current class not the a tag, otherwise the current li can’t be styled.
Sorry about the trouble here.
Indeed, the Nav link is having an issue with the placement of the .current class. Nav dropdown and Nav menu blocks should not pose a problem.