You're not an idiot - your dealership's Tech is. The tires
can (and should) be rotated side to side... just
not front to back, and it is recommended in the 2013 manual every 7,500 miles. Page 10-63. The factory RS wheels/tires are non-directional. If it were my car, I would go back and insist that they follow the GM recommendation to rotate the tires at the proper intervals.
"If the vehicle has non-directional tires, they should be rotated every 12 000 km/7,500 mi. See Maintenance Schedule on page 11‑2. Tires are rotated to achieve a uniform wear for all tires. The first rotation is the most important."
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2013 1SS/RS Coupe L99, Stainless Power Works LT Headers, SCT X4 Custom Tune from RDP, CAI Inc. Air Intake w/ Apex Scoop, VMAX CNC Ported Throttle Body, Solo Axle-Back Exhaust w/ J-pipes, Apex Catch Can, Husky Splash Guards, Heritage Grille, 3D Carbon Rear Spoiler, Oracle Chrome Turn Signal Bulbs, GM Reverse Light Trim Billets, Gorilla Black Locking Lugs, Emblem Pros Retro SS Badges/Custom Retro SS Kickplates/Under-hood Bowtie, 35% window Tint, Nitto Motivo Tires (6-8-18)