Note that Apple was able to use their slide to unlock design patent and that Apple in the linked curt case tired to "get patent-like protection for the idea of a graphical user interface [..]".

In this case it's not about the idea about a GUI but the very specific way the GUI was made wrt. non-functional aspects of the GUI.

And even if there is no enforceable design patent there is still copyright and trademark protection. E.g. look at the settings icon which is basically screams "lets change the settings icons just enough to not be a copyright infringement". That icon is trademarked by Apple and the JingOs variant has still quite many of the points which define the Apple trademark, enough to open potential for a case. (They have 3 connection from the gear ring to the center at the exact same position, a "dot" at the center, a inner ring (but just one color instead of an gear) and the gear background color doesn't stretch to the sides of the icon (I have no idea why they didn't change that, it would be more different and look better), they also replaced light silver with white. Anyway I would guess a trademark case for this detail has a good chance, especially given that this icon looks different enough to the other icons to not fit in, making it super clear that they somewhat forcefully wanted to make it look as much like Apple as possible. Instead of just using similar visual clues).

Didn't they win the billion dollar lawsuit when Samsung copied iOS almost as blatantly as this?

That case was a huge convoluted mess. If I understand it correctly the UI patent claims were rejected and the case came down to 3 hardware design patents, D618,677, D593,087, and D504,889. But the case is so involved you damn near need a law degree just to follow it.

That's the same suit that Apple claimed dominion over rounded corners, too, isn't it?