That is a cool stat though, because it tells a pretty good story about how good this World Series has been. 2 teams with 100-win record went pretty toe-to-toe right to the end, which is cool.
A 100-win season is a way of indicating the best teams in that particular season. I suppose it’s arbitrary in the sense that it could be 101 or 105 or whatever, but it wouldn’t make sense as a hallmark of the strongest teams if it were, say, 90 or 75. In the same way that 30 goals in a season for a striker is a hallmark of a really good season for that player. It isn’t arbitrary, because 20 goals would not show the same performance level.
The ‘World’ Series thing is a bit dumb but I’m always surprised that people pretend to care much about it.