The liner of the outer will be a tight wound coil under the plastic sheath ..... it shortens a little under compression but can open out as there's only the plastic sheath resisting stretch ..... the outer has a natural 'spring' ..... it may be this that's allowing the outer to expand.
On my old Harley which has a clutch that requires a serious pull I have a longitudinal clutch cable rather than a spring wound one to reduce 'lost motion' when the clutch is pulled that you can get as the spring-wound ones compress and shorten under load and expand again when the clutch is released.
K
