They can be swapped in, when the player is forced to, and discarded right after, for the original Pokmon that was in that spot
#10 Mana Vault - Golden Age I'm confused, but for this amount of mana it's worth it
Pikachu VMax #SWSH286 Pokemon Promo Keep track of your collection value over time
The size difference allows for quick visual distinction during play, no hesitation, no confusion
The true number is hard to estimate because most players see only a slice of the card pool at any given time the sets that were legal when they played, the cards their friends owned, and whatever showed up in tournaments they followed
Cards of varying sizes can create complications in grading and value assessment