Cover up, like diving tackle and wrap-up tackle, are underrated by slow builders IMO.
People will triple cap tackling but keep wrap-up at 0. Bort has said in the forums that one in wrap-up is noticably better than two points of tackling, which could mean more than 3, more than 4. Probably not more than 5 but it's only for non-diving tackles so who knows? But it's a good example of Bort confirming that a flat bonus SA isn't useless compared to one more point of an attribute.
It's the dude's last season. He's not looking to hit any caps anymore. There are no more SP payoffs. Bort didn't program the bonus to be so small that one point of carrying does more for fumble prevention than one point of cover up. He wants to stop fumbles, or cut them down (because it would be retarded to be able to never fumble). Cover Up is the better choice.
Maybe that's just faith but it seems pretty damn reasonable to me.