BOSS is just for fat. Good for horses who need to put on weight. Will help with overall coat condition, but no more than just plain ol' good nutrition, and most horses don't need all the extra calories.
The lady who wrote the article isn't doing anything. She's got some Photoshopped pictures and some others stolen from the Internet. There is no "miracle product" that will make a horse grow mane. It's mostly genetics with a slight impact of nutrition.
See this horse?
He gets the exact same grooming, feed, and care as this horse: