Box turtle sleeping behavior?

We have a mature WC male EBT we found near the house last year we decided to keep for "a while" and now we've had him over the winter.

Missing his front foot, but very tame and he has acclimated very well. We keep him on a few inches of damp topsoil mixed with shredded coconut and peat in a 30 gallon tank. He has dish of water big enough to get into, a hot spot under a floodlight on a ground level flat rock and a curved piece of bark that serves a hide and a place to burrow into.

Hot spot gets to about 115oF in the center, but is cooler as you move off axis and he has plenty of area to adjust. The damp soil under his bark at the coolest end is about 64oF and he seems comfortable, spending his time in various areas of the tank. He has learned to come out/forward when we talk to him and will readily take food from our fingers.

The thing that is odd is how he sleeps. He just lets his legs hang out in all directions and flops his head over in the dirt, closes his eyes and just goes to sleep all splayed out like that. His head is twisted around so it's laying sideways. First time I caught him doing this, I thought he had died. I touched him and startled us both, but now we see him do this all the time and it seems normal for him. Never seen anything like it, and I think "No wonder he lost a foot.".

He is alert and healthy, not fat, and eats worms, Dubia, melon, cantaloupe, berries, some greens, etc. and gets a good varied diet. We have four bearded dragons and the turtle gets fed much of what they eat, plus the worms. His bowel movements are normal. We keep his humidity up and his eyes are clean and clear. He can close his shell up normally, but just doesn't ever seem to be threatened enough to make it worth doing. When we reach for him, he is mainly trying to see what we are bringing him and is used to being repositioned in front of a food dish.

I've had sliders that stretch out in the 'sun', but that seems more 'natural' somehow and all of the EBTs I had as a kid slept with their shells mostly closed or at least with their extremities withdrawn.

Anyone see this behavior in BTs? Is it anything to be concerned with?