It doesn't make perfect sense. People are reading too much into this.
"By using the armor and weapons that you equip yourself with, you will generate "attachment points"* and when your attachment points reach 100% you will be able to convert them("them" means the points you've earned, not the gear) into "materia." This is known as "materia conversion." "Materia" is a crystallized form of the weapon and armor’s stats (Stats from the weapon, not the weapon itself) that the player has used and formed an attachment to. "