>>47409953He folds it up because it's a folding bike and hangs it on his backpack or something. If item balls are an actual thing, then that would mean shit like literal apples that fall off of trees in the middle of an island in the middle of a lake are shoved in Poke Balls by.... someone on a semi-frequent basis instead of just being an abstraction for various items lying on the floor.
Plus the existence of the Item Ball wouldn't explain shit like the player mistaking TWO Electrode, which are like 4 feet tall on average, for the Master Ball in the Aqua/Magma Hideout. Unless you are saying they put the Master Ball in an Item Ball.