Ryan Lorence Syfargo
2) the randomiser cards and role cards are different sizes so you can't accidentally shuffle them together. Randomiser are mtg size and the role cards are American board game size. I understand the card sizes could have been switched but I'm rather used to keeping American green, American mini yellow and mtg standard sleeves in stock for sleeving my games. Most games used the American sleeve size over euro so it doesn't bother me.
I think the OP's main point was why use American size for the role cards instead of MTG size, primarily for sleeving purposes. Most likely the American sized sleeves are probably not so easily found or more expensive?