Hahhahaa! That's FUNNY, Bruce. IN thirteen years I had the Prizm (first car I owned with a "space saver" spare), I used that tire twice in 285k miles ... and probably for a total of 40 miles. It showed no ... no ... signs of dry rot. Good grief, Bruce!
What are you talking about? When you have a teeny bit of dynamic toe-in and/or positive camber on the front drive tires, the outboard tread will wear just a wee bit faster than the inboard tread ... regardless of how you rotate the tires. It is also typical to have rear wheels on an FWD car set up for a small amount of static toe-in which results in a very slightly increase outboard tread wear.
Since space saver tires are the norm for many economy cars, I have only to concern myself with four wheel rotations on this Corolla. Back when I owned only RWD cars, the rotation schedule was still back to front, same side, no crossing. The spare became whatever old tire happened to end up in the trunk. I have NEVER bought a set of 5 tires.