JJ
ESA(CB) is always paid if the claimant met the Contributions Conditions and they are entitled to payment but if they are only entitled to ESA(IR) then there ESA claim will be closed and they will be expected to live off of their savings.
As to why this is the case, you will have to pose the question to the relevant Secretary of State.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems