Thanks for asking, Rupertw. Several past threads about it, here is one for your enjoyment. The issue is clustering of timeouts where a player continues to play his “winning” games, and does not play moves on his games headed for a loss and just lets all those losses timeout all at once. I don’t play players that timeout regularly because of the serial timeout rule, but that is a choice; in a tournament, one cannot select opponents.
If you notice a player that does serial timeouts or excessive timeouts, do report them to the Mods to investigate.