Ramifications of not claiming Income related ESA when Contribution Based claim ends

My client ‘s cont based ESA is stopping after 365 days. His partner gets IS for both of them , her entitlement is as a person getting paid CA.

If he claims Income Related ESA her IS will have to stop and they will get less money due to the lack of a couple rate Disability Premium.

If they opt to not claim income based ESA and just carry on as a couple on IS am I right in thinking that he will only have to do the WR Activity as although he isnt paid he will still be in the WRAG?