Because it's the Legion Zero banner, except that for some strange reason it's in your alliance's color and it pretends to be your alliance's banner.
Actually, if you think about it, it's kinda cool in its own way - since you can now parade around waving Molag Bal's faction banner
The intern hasn’t learnt to cut and paste yet. Just how to change colour pallets.
But, yes, it is ridiculous. Yet another great idea that players wanted, implemented with the minimal of effort by ZOS. So disappointing
.