ok, but, Google searches aside...which, c'mon; your recent searches dictate your subsequent results...the data I present is from a 'live' post here (in that the mods haven't taken it down) and one of the most well regarded series of books about all things 'farming'.
I'm not trying to be antagonistic. But, I've have cited the sources for my data and so far, I have gotten no citations from anyone about the 8 foot rule. Just 'pretty much everywhere' and 'I've never seen that low a number before'. That's not data. I'm just asking for sources of the given rule for 8'. I'm not in disagreement: I understand more space is better. Just back up your assertations with citations.
I'm doing my best to get this right and do the best by my birds. The most confounding thing about this journey has been the absolute lack of consistent data. To me, that's really interesting given how long humans have been domesticating fowl.
My search engine results for anything poultry related predominately leads me to these forums, which is where I got the 8 foot rule - it's what I found to be consistently recommended by BYCers. The One 6 foot rule I saw came from a site outside these forums. I was only commenting because I was floored you found a number that low, and on this site, of all places, where I found the 8 foot rule to be practically resoundingly unanimous back when I was looking it up for my own birds. You surprised the heck out of me, is all.