 So you just don't understand Polygroup Islands. Not a problem. This is a combination of polygroup inner with polygroup border. So when you left click on a polygon, every face that is the same color is gonna be affected by your action. Remember they have to be connected just because they're close or on the same side doesn't mean they're connected. They have to be touching each other to be considered part of the same island. Hope that helps. And as always, hope you have a fantastic day and I'll see you around.