I just think it's a personal preference for her. I have a female that always lays flat. I remember asking Adam about it a couple of years ago and asked him if he had any snakes that lay flat. He said he knew what I was talking about and had seen it before.

She does it year round, whether gravid or not, it's just how she prefers to lay. And when you take her out, she "rounds" up, just like any other snake. She's my only one that does it. She's gravid again this year and still my little pancake!