Do you address the posterior chain and hip stability with your clients when you have them train the core?
Don’t forget that the core musculature needs to stabilize the entire lumbo-pelvic system, not just the spine. If the posterior chain and other hip musculature are not up to snuff in stabilizing the pelvis, there will be either be too much squashing (clinical term) of the lumbar discs and facet joints, or overcompensation of the trunk muscles (typically QL, diaphragm, and psoas).