The skeleton shows no difference in the length of the thumb from the fingers.
Once more.
Here is the paper describing the find.
It contains this photograph of an
H. naledi hand:
They describe it as follows: "Palmar view on left; dorsal view on right. This hand was discovered in articulation and all bones are represented except for the pisiform. The proportions of digits are humanlike and visually apparent ..."
It has a long thumb, like a modern human or like
Australopithicus sediba, and unlike a chimp. It is not, however, as long as the fingers.
What it seems you are trying to do is gauge the length of the thumb by looking at a photograph where the bones of the hand have been taken apart and scattered on a table. (Close-up below.)
But obviously this has nothing to do with the actual proportions of the hand. If you dismembered
my hand, then you could send the distal phalange of my thumb through the mail until it was thousands of miles from my trapezium, and yet this would not prove anything about my anatomy.
Edited by Dr Adequate, : No reason given.