Safety isn't really a position that's quantified by stats. A lot of scouts will tell you that it's the toughest position to evaluate because they are so often so far away from the ball.
Earl Thomas for example, is irreplaceable in that Seattle defense just because of the nature of a single high defense and where it's weaknesses are. He erases those weaknesses in the seams because of his range. The number you look at there is how that pass defense struggled when he went down.
Similar deal with Kam in a different way. Seattle essentially has 4 linebackers on the field when they are in base with him. I have never seen a safety at the pro level be used in the run game like he is. At 225lbs. He takes on pulling guards... and wins.
Just looking at the names on that list, all of them have great versatility. Mathieu is like a swiss army knife in that scheme. I'd have his name on that list somewhere.