I don't know about that tire size on the stock rim but something else to consider is that you may have to order the matching tire and wait for days or longer. A full sized spare relieves the possibility of riding an off sized tire/wheel during that wait. Its an investment some don't consider...
I made an appointment for my first oil change and they tried to bill me for it. I told them I had purchased a maintenance plan and they said it wasn't in the system. So I pulled out the contract and said, either honor this or write me a check for $2k. They'll probably try to pull this again...