Warrior was the generic catch-all type for things without an obvious type for a long time. (Hence why cards like Stuffed Animal and Hungry Burger are also Warrior.) They vary that a bit more now, though seem to use Fairy more than anything else for it these days.
It's probably cybernetically-enhanced armour. (SUPER Roboyarou's certainly is, as seen in Cybernetic Zone.) The fact it says it "upgrades" also hints at it. Not sure why that of all things is something you decided to question.