Crazy. Never heard that before, but it makes sense.
I looked into it because my Focus RS is AWD, so I wanted to see what options were out there.
I looked into it when I considered buying the RS since it was AWD and I had heard about the 4 tires thing.
If the tires were in good enough shape, I'd just shave a tire, even though its essentially wasting some money. Better than buying 4 new tires and throwing 3 good ones away.
Makes sense but the shop he's at does not offer that service, so what they advised him to do was correct based on their capabilities
If I had a spare, I'd put that spare on the car, drive it over to Discount Tire, and buy a shaved tire there.
Only problem is from a recent search it looks like not all DT's can shave a tire, and might have to order a shaved tire from the warehouse. So thats down time. Tire-rack is the same, they shave it at the warehouse and ship it out.
Temp use on the spare shouldn't damage anything. A few days waiting for a shaved tire shouldn't be a problem.