The biggest misconception in the fitness world is that 6 pack abs is equal to strong core.
Six pack abs, outcome of crunching and working out, lot of transversus abdominis, is just ONE muscle group in a group of 10+ big and small muscles that form our core.
Ironically, there is an equal if not large amount of core muscles at the back of our body, wrapped in with our spine. Weakness or improper use or lack of use of core muscles in the back is the primary reason for issues with the spine.
In fact, wrong posture, is a chicken egg problem of wrong posture and weak muscles. Often people with weak back muscles have wrong posture, and folks with wrong posture (thus overusing, underusing and misusing certain muscle groups) have weak muscles.
A stable inversion typically works each and every big small core muscles in your torso. In a handstand, multifidus, internal and external obliques, rectus abdominis, erector spinae, longissimus thoracis, quadratus lumborum come together to place, hold, and balance is body.