A group is not a smart group and therefore this is true, just like a smart group is not a group and documents are neither tags nor (smart) groups. And therefore this condition matches all kinds of items.
Oh, not much really. It’s more a visual nag: “Look at me!”, and a priority when I process my inbox. I have another smart rule that changes the label to “One Month” after 30 days. That is when I decide on the spot to either process it, or delete it. I make it a point to make an immediate decision. Because if I can’t decide what to do with it, or where to move the file after a month, it is not worth keeping.