I think the fact that the Canon overheats when recording internally could also mean that not oversampling is causing the heat but the compression. Cause that's the only thing the cam is not doing when recording to the Ninja V. Maybe there's a separate chip for H.265 encoding somewhere on the board that overheats quickly. But this would also not explain the long cool down times. But H.264 for example is meanwhile encoded by the GPU on computers and does not affect the CPU much.