Gauff sat on her sideline bench for a bit in the course of the break in the match, eating fruit out of a plastic container, before hitting a number of follow serves. Not during a 40-shot change that ultimately helped resolve the result. And not, most distracting of all, when her US Open semifinal towards Karolina Muchova was interrupted for 50 minutes by environmental activists — one of whom glued his naked ft to the concrete ground within the stands. It has been somewhat apparent for quite some time that Gauff is no ordinary teenager. Gauff, a 19-year-old from Florida,…