"Big Navi" won't need that huge cooler. If it is a 80CU chip, it would be less than twice the size of the 5700XT. Almost half of the RTX 3900. That also affects power consumption and heat. If it is a 62CU chip (which I believe will be more likely) physically same size as the Xbox X series APU (the APU is 54CU with 2CU cut off plus CPU etc subsystems) so a standard cooler will do because it wouldn't need that much power.