I’m not conviced that deprivation is an issue here.
There does not seem to be much doubt that they have to sell-up. If they were to move they would have to either:
Find a property with suitable adaptations or,
Find a property and a landlord willing to make the adaptations (and probably pay more rent as a result).
Find a property and a landlord who is prepared to allow them to make the adaptations themselves.
Given the figures you have quoted it seems an arrangement has been made to clear the debts and retain a place to live.
Their property needs sound like they are fairly specific and I suspect that there are few suitable properties available. If this is the case then I really cannot see how the tenancy is taking advantage of the scheme either.