Does the Spear Wall passive, which increases block amount against melee by 7%/15%, only apply when you have a shield raised? So is this passive really meant to aid 1H+S players? Or is it truly passive and you just take 7%/15% less melee damage?

In other words, is this an aid to your vanilla right-mouse-click blocking, or is this like some kind of magical barrier that automatically reduces melee damage?