Short answer
The wrong heel compensates. The right heel aligns.
An unstable heel forces the lumbar spine to compensate — the pelvis tilts forward, the lower back overextends, and the muscles along the spine work to hold a position the shoe should be providing. Over hours, that becomes pain.
A structured heel with controlled pitch places the pelvis in a more neutral position. The spine stacks without overextension. The load distributes across the kinetic chain instead of concentrating at L4-L5.
This is not therapeutic advice. But the mechanical principle is simple: a shoe that holds the foot in position reduces what the back has to do. Persistent pain requires professional assessment.
This is not medical advice. Consult a specialist for persistent discomfort.