It is crazy because if you have a >13" laptop, this won't fit in the cabin bag. Taking the rules literally implies that if you want your >13" laptop in the cabin, you have to buy priority AND use your large cabin bag allowance to carry it. Plus, if you want to travel only with your >13" laptop bag and nothing else, you are stuck: you can't carry it on board because it's too big for the small bag allowance, and you can't obviously have it placed in the hold all by itself. How is this not crazy?