Glaives an naginata were used as both thrusting and slashing weapons. The entire point of them was their versatility as opposed to a normal spear and they could pretty much be used as a longer ranged straightsword. That being said, it would look pretty silly to see a terraria character swinging a spear over their head, so I'd love to see you try to come up with a method of coding these to slash as well as poke, by all means we have a suggestion channel in our discord. In the base game, the Adamantite Glaive is a weapon which can be made and it functions as a spear, just like these weapons.