Why is this tagged Error?

My guess is the only visible toe could be seen as a big toe, which would be an error. But without the other toes to compare, there's nothing saying that isn't her baby toe.

Well, the bulge of the toe joint makes it look to be the big toe, in my eyes.

Also, the way he drew the skin-fold line almost all the way to the heel just isn't right.

It just looks 'unfinished' instead of 'error' to me. Her hand is like that too.