Wouldn't that type of hold be effective against the strongest if they were relatively the same size? Being pinned in that kind of way, defies strength, because in practice it uses the person's strength against the person. Don't believe it? Look at Gordon Ryan, he made the strongest man in the world tap. It had nothing to do with strength. Demetrius Johnson a guy weighing 140 lbs at about 5'3" recently defeated a 6 plus foot 300 plus pound man.
Black Panther in that scene used one of those exact moves. The Surfer could have gone intangible at any time, which begs the question of who was actually in control?
Physically however, without using his powers, he was legitimately pinned.