I only keep T. yangi but I have one with hind foot that only has four toes and one curling outwards in a similar manner. It doesn't seem to cause any issues and the foot is fully functional, has been this way since I got it as a tiny juvenile two years ago. My other has one slightly atypical foot too, but it's hard to describe because it is very minor, it's like the gap between the two longest toes is slightly wider than usual. I suspect it is something environmental and not genetic, like sibling foot biting as larvae or nutrition before they were switched onto earthworms by the breeder, but I can't be sure. Regardless it hasn't changed or caused issues.