Staying in low fat percentage range for long time can f up your hormonal and other systems. Not saying its the case here but something to take in considerations for those staying lean naturally
Yeah, if you're a bodybuilder or marathon runner carrying a single digit body fat percentage - which is not something the average person is going to "accidentally" do.
Everyone else is probably safe trying to get as lean as possible so long as they're not malnourished.
10-15% and you have somewhat defined sixpack. Lower range of that continuously naturally and you might have yourself a problem. You only have to be somewhat enthusiastic about fitness and watch what you eat to get there. Not that uncommon these days
15% is pretty damn flabby though. Unless you have a very unique body composition and putting your fat into say your legs and butt (like women typically do) youll def have a soft doughnut around your waistline and no way you have six pack abs. Its more in the below 10% bf when you actually can start to dream about the 6pack if you actually have the muscle.
You've seen some misrepresented data. You commonly see fit people saying they have 6 or 8% fat % when they are closer to +12%. Most methods to determinate fat percentage are hilariously inaccurate. Look it up.
15% and you see hints of sixpack (clear outline) for most people who train.
Everyone else is probably safe trying to get as lean as possible so long as they're not malnourished.