I'm sure it was a mistake - since by default when you create a new tournament, "All Games" is the choice. (I can't tell you how many of my "Fast Start" tournament I had first made as "all games" by accident)

BUT NOW (As of BK2.0) when you create a new tournament, it does not take you back to what you just created - but takes you back to the main tournament page, so it is easy to not see the mistake until it is too late and people have started to sign up.

And the only way to fix the mistake is to remove the whole tournament, and create a new tournament.