Not sure what you mean, It's been part of the sport for decades. A tire that gets hot often will smooth off and seal (glaze) the outside of it and therefore not be spongy and gripping on dirt. Grinding a couple thousands off the top of each block will revitalize that stickiness and furthermore regain the groove edges which also dig into the dirt.
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Some teams even put talcum or baby powder into the rubber after doing it. This I am unsure of what it accomplishes.

Worked on LM's in the 80s. We did it weather we thought it needed it or not. If you don't do it, your either gonna throw a new tire on every race or your going to go out there and just spin your tires because they are not going to get the grip they were designed to get.

Setups get you toward the front, Tires win you races. The team with the best Tire Man, Stagger, compound, grooving and siping is going to be on the podium. Grinding is a must if you plan to re-use a tire. You just don't run without doing it. Sometimes you'll see a a guy after the race with a laser thermometer. Or just go and put their hand on both rear tires. The closer you can get both rear tires in temp. The better they'll run as long as they aren't getting too hot.