Basically it says..
"Each level of goal line blocker gives a 2% to strength, agility, and blocking on rushing plays inside the 5 yard line when this player is blocking on the line"
Technically, TEs are on the line as well..
"Each level of goal line blocker gives a 2% to strength, agility, and blocking on rushing plays inside the 5 yard line when this player is blocking on the line"
Technically, TEs are on the line as well..