Didn't see these hairs on the website but didn't look
hard.  They do appear on our cats.

Based on nothing but my own observation, I think that
these hairs are sensory fibers most useful to the cat
for registering his steps.  When a cat walks, his back
feet step where his front feet have been, left on left
and right on right.  Cat tracks show a single row of
alternating marks, unlike dogs or coyotes who leave two
rows of alternating marks, one made by the front feet
and one by the rear, though often mixed together.  I
think that the cat's rear foot comes up to touch the
wrist hairs and is set down near the front foot.

One of our cats, deficient in these hairs, is extremely
clumsy climbing and walking on fences and such.  I
think that, because the hairs on the foreleg let the
cat move the rear foot to the same place as the front
foot, if the front foot finds a stable location, then
the rear foot can use that location as well.

Hmmmmmmmmm. I guess I'll have to check my cats paws! :c)

Judy