Pleased for you.
So if we're coming across as negative, well sorry it's infinite expectations tempered by curiosity. The puzzle is it seems math predicts it's too big for no reason, and also if you were to go to 15W if you were to have made it to say 18W you could have made that 18W as say IQ2 to please the Quick charge use, or 9V 2A to please some of the PD users. So to make it so big and not be either just seems like a lost opportunity.
Admittedly we don't work for you, don't have a PhD in electronics so it's still amateur commentary.
I bought many Fusion 5000, they perfectly suit the type of person who does not remember to recharge a powerbank so I just give them one of them and appropriate cable and it does the remembering for them. I happen to have a 9V 2A 18W device is so very near your 15W it hurts.