It's just leverage to get Apple to settle without waiting for next year's trial(s). Just like the Avago LBO was leverage to force Qualcomm to settle on Apple's terms.

Except for the fact that no current model Apple devices use their chip...

And the China ban is not actually about the chip in use but some software feature in older OSs

Actually suing Apple about the stuff they have a conflict over is lethal as they're doomed if they lose a trial over it and their position isn't that secure since they're already getting sued all over the place for their tactics around wireless patents.