perfect essence of battle functionality issue

a perfect essence of battle will let you add +attack skills to a crossbow but all crossbow skills are considered projectiles. so is the essence supposed to convert if not why does it allow you to add the stat to a projectile only item?

There are some non projectile skills with the attack tag that you can use while having a crossbow equipped. Some that come to mind are buffs (Heralds, Wind Dancer) and some Marks.