It's rare, indeed. Very few people to be privileged to have that, even with their closest people.
And it's not only about judgement, but also about the weight of what you could say, how you may want to protect them from what you think.
You don't realize how rare it is to feel completely unjudged until you find a friend you don't have to edit yourself around. You can ramble, contradict yourself, change your mind mid-sentence, and still feel accepted.
You don't worry about sounding stupid or dramatic. You don't rehearse what you're going to say. You just speak. And being that unguarded with someone changes the way you breathe in the world.