Vaxalon said:
Yes, necessarily, Karinsdad.
It's part of the tower shield rules that whatever cover benefit you get from hiding behind it is also bestowed on people on the other side of the shield.
The point is that cover is cover.
It matters not if the source is a wall, a tree, a rock, or a tower shield.
In the example I gave, the Giant had 100% cover from the Man with non-reach melee weapons since the Man could not reach above the top of the wall and could not reach through the wall and for no other reason.
The Man, on the other hand, had less cover since the Giant could attack from above, hence, the wall might give the Man 50% cover. The Giant is not attacking from the front, but from above.
This is really no different than a Man across a 5 foot wide pit where the Giant can reach the Man, but the Man cannot reach the Giant with non-reach melee weapons except the Man has 0% cover in this case. The Giant also has 0% cover, but it’s basically the same as if he had 100% cover since the Man cannot reach him.
The cover rules are explicitly left to DM discretion due to the wide variety of possible cover situations. I just happened to mention one where the way we normally think of Tower Shield cover does not necessarily hold.
DND cover rules, just like any other DND rule, should not be a straight jacket against common sense.