As I said, it's simply a ratio I can compare to based on what I know of other people's results as well. It's more accurate than me just making a good guess by estimating myself how much a person of that height may weigh on average, since it's an actual calculation of what I'm guessnig. You can disagree with me all you want but if you're going to make an estimate of how much a person should weigh, I see no reason that height wouldn't be the first, maybe most important factor that differs a person's weight. Again, reinforcing the fact that I'm not making an accurate judgement as to if his weight is healthy, it's simply a stat for me to quickly compare since I clearly don't have access to medical professionals to assess his weight. It's better than nothing is all I'm saying.
As for where you said it doesn't apply the square cube law I believe I understand. However, I've already said that it's a simply height to weight ratio and is only as accurate as it sounds lol. I see no reason it needs to apply that law because in order for it to do so wouldn't it need to include measurements like waist size? And wouldn't that defeat the purpose since waist size and other measurements would only vary as weight does, which is already included in the formula. Maybe I'm thinking of it wrong in which case you can feel free to correct me.
As for what you said about when it was invented, I wouldn't disregard anything's use just because of when or even how it was discovered/invented. It doesn't mean nothing viable could have come from it, in my opinion.
Besides, Coca Cola was invented not long after that time so the 1800's can't be so bad
.