I've watched the replay of this hit 5 times. I see a lot of commentary stating that the hit "caused Carlo's head to impact the boards."
"Their first test was whether the hit satisfied the criteria for an illegal hit to the head. That wasn't a solid case, given that Carlo's head may not have been the primary point of contact on the hit and that Wilson appeared to attempt a full body check on the play."
Caps' Wilson gets in-person hearing for Carlo hit
The wording seems to consistently be avoiding the truth: the primary point of contact was Carlo's head, which was impacted by Wilson's upper arm/tricep, and the head then hit the glass.
How is this hard to understand? A dirty player smoked Carlo directly in the side of the head, against the boards, when he was vulnerable. Wilson should get 40 for this one when compounded with the Sundqvist suspension/hit.