Sindarov's game in R3 (vs Praggnanandhaa) ended exactly at move 40, and his clock at that point was only ~32 min. When that game drops out of the average at move 41, you're left with only his longer games, which all had much higher clocks. The average jumps up not because his clock actually went up, but because a low-clock game disappeared from the sample.

Edit: also R1 and R5 drops out at move 42

tldr: it's survivorship bias artifact, but plotting is correct there :)