It is NOT a fabric Kelly. It is very much a cover for the bag that was available at podium. It is NOT a push offer item and it is also NOT waterproof. In short, it is literally a cover, one that when placed on the bag, make accessing items in the bag rather difficult.According to the AW18 thread, this is not a separate cover, it is a type of fabric Kelly, which explains why it looks sort of like a toile Kelly.
It was marketed at the podium as something for one to use when one takes their bag to safari.
My 2 cents: There has been quite a few 3rd party bag covers available and H is just capitalizing on that market since people are spending on those bag covers anyway. It's the same logic with the shoulder straps. Why not? We can profit from it too.