I think @Coloma is right that the scale has ascended towards helicopter over the decades for many, and the scale means different things depending on the decade and of course the location and norms of place and time.
I can hardly believe how controlling, restricting, and limiting some of the attitudes have become like, compared to how it was for me growing up in the 1970’s and 1980’s. Most of the changes seem like terrible mistakes to me.
I’m not sure anyway what to make of the proposed scale. I think my parents were mostly very responsible and concerned, and would intervene strongly if they had to, but they very rarely had to, and so mostly did not. My dad was more allowing and less concerned and vigilant that my mom was, but both of them would intervene if there was a problem or concern, but there usually wasn’t much of any concern. There was a strong mutual trust & respect thing going on that mostly worked quite well. But even in contrast to their generation growing up, there had been increases in controls and limits placed on kids, in some ways, though of course even they remember some exceptions – kids who were tightly monitored and rulebound.
I’m not sure what maximum free range would be. I’d say my dad was maybe an 8 on the free range scale, and my mom more like a 6, where zero would be neutral and helicopter would be up to 10 in the opposite direction.
So far I’ve only been an unofficial step-father, and in that role I naturally followed the mother’s mode, and I’d say she was maybe a 7 free range. My tendency is to maybe be a 7.5, but again I think it’s pretty hard to know what any scale actually means.
I agree with my parents that all rules should have a reason. I think kids should have a right to privacy and freedom unless/until there’s a serious reason to intervene. I think it works much better at least with most of the kids I’ve known to develop a healthy allowing trust & respect and openness, as opposed to trying to monitor and control things. I realize there are times to be vigilant and intervene though, which would call for something else, but I think the best way to not need that is to only go there when needed.