What Rob says!
Your wrist looks like it has a LOT of bend.
When I play power chords, my wrist is bent considerably less than what you see in Justin’s photo there. I keep my elbow low & tucked close to my body with about a 30 degree up-angle to the neck of the guitar & don’t have any wrist pain. That said, we’re all built differently so this may not work for you… I would try to limit the wrist angle though!
Tod
PS Took me a few minutes but I remembered & found this advice Fretting Hand Wrist Position for Better Finger Reach & No Wrist Pain in another thread (same video in that post) that may be useful!