This might just be at my rink, but alot of the skaters here are doing sit spins and backsits with their legs bent in and sort of wrapped? Like the begining free-leg position of a scratch spin, but in a sit spin? My coach always told me to keep my leg straight, and that it's more "technically correct" for it to be straight, not wrapped. But the bent leg in the sit spin seems to withstand good in competiton.
Sounds like a variation. There is the bent leg "out to the side" - a broken leg spin; there's the free leg wrapped behind and "under" the spinning leg - we call it a squeegee spin, but, there are other names for it ... the pancake, where the free leg lies across the spinning leg and the skater's upper body is bent down on the leg ... there are a ton of different variations on the sit spin. The crucial point is whether the sit position is obtained, which requires that the thigh of the spinning leg be parallel or below parallel to the ice ...
Skaters use the variations to bump points for levels, and also because, well, they look cool and are often more difficult than a basic sit. However, that said, a skater should be able to do a solid basic sit spin.