They used two different materials (maybe more??)
On the ones I have (some from my original 1971 doors, some from donor doors of another year) it happens that the different materials are on the two different types of the brackets. So it could be a 'type of bracket' thing, or a 'depends on year' thing

Either way, these are definitely different material - one is more 'hairy' (right)and one is more 'fuzzy' (left)

I think you can see both in the above posted pics, as well as my pic below.
If you need to see the detail click on the attachment to get the full sized pic, it is pretty clear.