The issue here is users complaining that the phones get too hot to handle, which immediately eliminated conductivity. A thermal conductivity problem would've looked like the phone overheating without the outside getting too hot to handle. (picture the circuit board inside a thermos)

that's not necessarily true. Heat has to go somewhere eventually. It could be that the CPU is much hotter than the temperatures felt on the frame. but yea, if the cpu is 45 C and the frame is 40 C, you'd be right.