Groups are a social feature meant to join people together so they can compare their bracket performance.
If you don't want everyone to join your group, you can set it to private and make sure that only people you invite are going to be able to join.
Each group has it's own local standings.
The group standings have relevance ONLY inside the group, and do not matter or count towards the global results of the user.
Your rank in the group standings do not qualify you for media partner prizes. Your rank in the cumulatve standings is the only quantifier that qualifies you for media partner prizes.
A group owner cannot award prizes nor can it promise it's members that they will qualify for any media partner prize.
By joining a group, public or private, you acknowledge all the above.