I believe the key element here is "if they promised to comply with the rules". Since Epic has already filed an appeal, they don't seem to express a lot of willingness to comply with the rules.
In your quote Cook said "if they abided by the rules" but in the Sweeney letter you linked to he said "Epic promises that it will adhere to Apple’s guidelines". Sweeney didn't say they actually did it.
Also, the daringfireball article includes the letter you linked to and covered this topic.