Ever since Bohemian Hussite Wagons which cause projectiles to deal less damage to units after the projectile passes through the model hitbox, it is weird that walls have not given similar treatment, allowing units close to the wall to take less or no damage from enemies trying to attack them through walls, but only if the units are close to the wall segment. Would also expect Castles to offer similar protection to units near it, since they’re buildings meant to be used for cover, but Watch Towers are so small so they wouldn’t.
Since game already simplifies visuals, units near walls can be considered to be taking cover behind the walls.
Would attacking units lose wall protection? I dunno, losing it when attacking would be like the units popping up behind cover of the wall to fire arrows at enemies.
Although that would entail balance changes to whole wall system. Don’t think Siege weapons attacking buildings behind walls would be affected since the whole wall protecting you is for units and not buildings, so as to not over complicate walls with Siege weapons.