That's completely besides the point. Flats and crashes are an ever present risk throughout the Tour, however, gravel simply increases (unnessecarily and rather unwisely in my view) the chances for them to occur. Look, it's not Strade Bianche, which is a specialized, consciously contrived vintage-themed modern event. It's the Tour de France in which you want to see all the Bigs make it to fight the great mountain and TT battles of week three. Mostly nobody wants to see a Pogacar, a Vingegaard, an Evenepoel or Roglic (to name the only the front-runners), be taken out of the GC battle or the entire race, because of this type of "gimmick" stage. Doubtless it will be entertaining and if all goes well people will surely be singing its praises. But can you possibly imagine the consequences for the Tour if say Pogacar crashes out, because somebody clipped his handlebars going into a gravel section at 65 kph? I don't think ASO or the fans shall be so entertained then.