No, the other forms require sites to opt-in whereas this just sends the information whether the site wants/needs it or not. There is plenty of harm in just thi

No, the other forms require sites to opt-in whereas this just sends the information whether the site wants/needs it or not. There is plenty of harm in just this fact alone, because tracking via the other methods is transparent: you know sites are doing internal tracking if you see them being used. With referral information sent by default you have no idea whether the site uses the information or just ignores it. Either way the important thing shouldn't be how much referral information should be sent (because clearly people disagree on that). Rather all browsers should let you customize this if you want to.