I agree about the Music Explorer tab and thats because resizing support is not implemented in that tab and i will leave that as is.
For the Music tab, on my screen the now playing bar is 3/4 of the screen height but i cant drag it above the header ie. works as expected.
I will agree that if you resize the application window height, you can make the now playing bar overlap the header - thats why i asked how you were doing this. But in no circumstance can i drag the bar beyond the expected bounds.