I asked Charlie about this and he did indeed use Cree.
If you notice, Charlie wraps with the concave side up. The fibers slanting up, rather than down, help prevent the accidental catching of stray fibers.
Personally, I like my hackle with the fibers slanting down. I can’t remember which mag it was, but A.K. Best had an article on how to tie off dry flies. Hopefully, I can explain it.
(Assumes a right handed tyer)
After taking your final wrap, keep the hackle in your right hand. Bring the tip of the hackle facing all the way back over the end of the hook. (tip should be facing left)
With the fingers on your left hand, pull back on all the feathers including the hackle. Do not let go of the hackle tip with your right hand.
Next, bring the hackle tip forward over the eye. Do not release any of the pressure from your left fingers. The pressure from your left fingers will create a “V” notch where some fibers face backwards and some face forward. If any fibers are poking a little bit out from your left fingers (kind of half in/half out), use your bodkin to release them facing forward.
Tie off on that perfect V notch. Nothing gets trapped.