I would not write it just like that, because some players in this cup and in my group did not know that a different scheme was being used until I said about it, and secondly, already one game in the 4th group was played not according to the cup scheme.
You should have written that the scheme is different from the usual - in the description of the cup, because the name is the same.
It’s your fault that you didn’t convey the information to the players correctly, you don’t need to be so toxic.