Hi,
I agree with limbin.

The question i always ask myself when i choose a treatment is "why would this help my patient?".

In spondylolithesis, there is a physical defect allowing bones to move where they don't usually move. That is, there is usually too much movement.

Traction is essentially stretching. Or mobilisation in a craniocaudad direction. Either way, it will INCREASE movement which is not necessarily desirable.

Short term may be helpful as outlined by limbin above. But long term, research shows that core stability exercises are the recommended treatment action.

As limbin says, it makes sense. Stabilising hypermobile segments is sensible. Mobilising hypermobile segments is not.

Hope that helps!