I’ve been known to shave tires for racing. I usually get some puzzled looks when I explain why I just cut off half the tread.
The RA-1 is one of the few tires where the manufacturer openly recommends shaving for better performance. For their next generation, the R-888, Toyo recommended customers go full-tread. I think this article does a good job of explaining the pros and cons: Buffing or shaving grooved tyres used for motor sport.
Photo courtesy of Toyo Tire
Usually it takes some phone calls or face time with the manufacturer’s motorsports guys. Some will say to shave them, others say not to; if you are lucky they may tell you why. Some tires have consistent grip from full-tread to chords, others increase grip as they wear, while others decrease. Tread blocks may add forgiveness to the tire where shaved tires may snap. For the low-horsepower guys, the decreased diameter or reduction can pay dividends. The high-horsepower guys might like the extra gearing. Weight
With so many factors to consider, it is just another thing to test when trying to turn in a lower time than your competition.