It seems as though the coach was attempting to count pitches and obviously missed a few pitches. I would guess, if there was nobody collaborating as to the number of pitches thrown. WHO was the official in charge of counting pitches? I've seen those tracking be over and below official counts. There should be a single source for the official count. It could be determined by the official book which is supposed to be an unbiased off field official.
Strangely enough, this borders on lack of sportsmanship and doing the right thing. An adult had the opportunity to inform the Umpire(s) of the impending pitch of 100. Instead, kept the information to themselves for a biased gain/win, albeit by technicality. I can only imagine the persons jubilance in the "gotcha" moment. Sad.