That is the most nonsensical thing I have ever heard. 1) The camera doesn't have any trouble shooting 30fps video at 0°C/32°F but room temperature operation for 24fps video is too cold? 2) Heat = noise. You NEVER want more heat, that is why camera's have heatsinks, fans, etc.
I just got a D750 yesterday and I'm very impressed with it's performance. Lots of detail, no moire, great dynamic range. I have it matched with the optically stablized Tamron 24-70mm f/2.8 and the results are excellent.