That's nothing new, many cars today with the space saver spare do not have enough space in the wheel well to hold a regular sized tire. You wouldn't need the space saver tire if it did.

My X5 has a 17" spare in case any of the 18" tires needs to be changed. The dealer explained that that was usually the case. It would seem that the implicit idea is that the spare tire is a temporary in most cases good enough to get you to the next service area.