This is definitely true — 9×9 is too small for a real game. But 13×13 is a much better compromise and I would recommend that to players who have outgrown the 9×

This is definitely true — 9×9 is too small for a real game. But 13×13 is a much better compromise and I would recommend that to players who have outgrown the 9×9 but still don't need to sit through a two-hour game before they learn from each mistake. (To be precise, the problem with 9×9 is that often after just a few moves the board is divided into a white half and a black half, and the rest of the game is a yose to decide whose half is larger. I'm sure someone can counterargue that if played expertly, 9×9 is a fascinating and highly skilled game; but in general it's going to lack a lot of the situations you can encounter in a full game of Go.)