Ran into this issue replacing a single unrepairable tire on a VW R32 All-Wheel drive. Had TireRack shave the tire down a few mm to match the slightly worn originals and all good. Local chain retailer (won't name them) insisted I had to buy four new tires. Had same issue with a Merc 4MATIC a few years before and not aware this was an option so bit the bullet and ate the cost of four new replacement tires. I recall I was given $25 off each of the three remaining low mileage tires. Michigan roads - Governor ran on the platform - "Fix the dam roads!" and won. Anyone thinking it's wise to scrimp on road repairs will regret it sooner or later due to destroyed tires or worst, annihilated rims. Then it really does get costly. And good luck matching your remaining rims on an older vehicle.