Hosts of Tournaments or Games can Invite players to their game or Tournament. These players are not required to meet Open Seat Prerequisites, and can Forward Invites in a Tournament with the setting enabled.
Keep In mind that players invited still have to join or decline before they are accepted, and someone that declines will not be replaced. Open Seats in regular Games will replace themselves immediately if the Player that had previously Joined changes their mind and Declines. In an Open Tournament these players will show up as Declined.