Premiere getting the thing to overheat sounds to me like Premiere manages to make full use of both the CPU and GPU at the same time, which, on non-overheating hardware, is the best way to achieve maximum throughput.
This is not that easy to do; it takes quite some effort to make sure that the CPU never has to wait for the GPU and the GPU never has to wait for the CPU. It sounds like the other video editing apps were all running slightly sub-optimally for properly-designed hardware.
