I agree that this is a stupid place to put it. At least it's encapsulated with a plastic cover to keep it dry. Also you would not have that nifty tray and storage space under the floor cover. You also have roadside assistance to help you do this.
Probably the best place for it but in winter up here in the north with all the snow and salt -- inside the car would be best.I like that it's under the car, because when I have the back full of baby stuff, I don't have to empty the trunk to get the tire out.