Sorry, i've beginning to realized in comparison there are alot of miscategorization in that spot as I explored. I'm not very familiar with the site and was confused so forget it. Technically it can be defined as stock image since you are allowed viewer to use the image for whatever recreation of the pictures, but I don't feel it's defined enough to be studied by. It seems like this image is helpful as pointing out observations such as where the joint is in various position but as mentioned in your title, it is a practice hand.
but only together with the others! its in fact harder to curl the pinkie back while reaching out with the other fingers especially the ring finger.. it curls in if you relax it, that i true. but if you do so all the fingers do so aswell. or atleast the ring finger because they are attached to the same sinew.