That's my 2cents worth. In addition to recently fed or sick, gravid females prefer additional heat. I agree it is important for all reptiles to have a temp. Ectotherms are incredible and this mammal never ceases to be amazed what a little heat will do for a frozen croc. Now having said that, that is the point that worries me.
People think it is a light switch, instantaneous.
As remarkable as it is there are points of no return from cold or from heat. I call that their body core temp. That temp. is not reach in a few minutes but over a period of time being exposed to a heat or cold extreme that is to much for that particular animal. When that point is reached you can't save that animal. And to be honest with my experience cold is a little more forgiving than heat.