I've never had my girl constrict and not eat live nut with f/t it was like 50/50. I've even made my girl constrict the same mouse twice and still wouldn't eat it. She just won't do it. Then she would constrict and never eat and they were warm defrosted and not cooked. She just won't eat f/t. So I feel that a snake will always constrict to an extent if they are hungry do to instinct but won't always eat it. So just from my experience. My snake is very very picky and I wouldn't be suprised if this snake is doing the same thing. But with its age and previous owner it may like to be covered or lights on or off or who knows. They all have their own personalities and preferences. So you just have to figure them out and experiment.