I would agree with that. Amongst the Supra owners with JDM cars, the general concensus was the same - stick to SUL / Optimax, as the ECU has a hard time dealing with the normal stuff. The Supra is another highly tuneable car - capable of an easy 400 - 450 brake with basic mods, and running around on standard grade fuel with increased boost levels is a bit of a no-no.
Mind you, even my UK spec car benefitted from running on the stuff - it was definitely smoother and more economic that when using normal 95 RON. I'd say use SUL / Opti whenever you can, and carry a couple of bottles of octane booster with you for the times when you can't