My problem with this game's plates is how they are actually USELESS because you get Arceus when you get them all, Legend Plate included, you never have the chance to go with Arceus and think which plate you should use, ask yourself if you should try getting a new one to fight a strong pokemon with supereffective Judgement, etc.
No, nothing like that, you just get Arceus and have zero reason to ignore the Legend Plate, the other ones are irrelevant. They should have done a single item slot that includes all plates and have it increase numbers everytime you get a new plate (kinda like the Spiritomb stone, just with a bag of plates) then once you beat Arceus he fuses all your plates into the Legends Plate. There you go, bloated key items inventary problem solver