All claims to ANY benefit are financially assessed against strict criteria.
These are the current rules
“ As of 15 May 2019, mixed age couples are no longer able to choose whether they claim Universal Credit, Pension Credit or pension-age Housing Benefit. Instead, mixed age couples can only claim Universal Credit until they both reach State Pension age. April 2024”
Sometimes people are a bit confused as to which benefits they are actually receiving. Both UC and Pension Credits are means tested, so although it sounds wrong, and all who can work should work, in this case if he was medically retired she may well be his main carer.