The first thing to remember about posture, for most peoples only one piece of the puzzle. There are plenty of people with relatively good posture and in significant pain, while others with posture experience very little pain. Pain, especially chronic pain is very complex, costing billions of dollars every year to the Australian.
https://www.sydneychiroandmassage.com.au/how-chiropractors-use-posture-to-scam-pain-sufferers/