EEA Nationals Acquiring Permanent Residence and Documents Certifying Permenant Residence

I am looking for views on EEA nationals acquiring a permanent right of residence and whether the documents certifying permanent residence are sufficient enough evidence that a claimant has fulfilled the criteria to obtain a permanent right to reside and therefore no longer be a person from abroad. Also looking for anyone with similar cases that are coming across the same issues.

I have recently represented at an appeal for a family member (daughter) of an EEA national who has a document certifying permenant residence issued 2008. The appeal was a right to reside case where the daughter has been refused ESA on the grounds she has no right to reside. The case for the client was that her father had the document certifying permanent residence, presumably giving him permanent right of residence in the UK and so she could then aqcuire permanent right of residence as a family member of a former worker who is no longer working due to being incapacitated and that has permanent residence status. The Father arrived in 1997 worked for 3-4 years then had to stop work due to being incapacitated and so must have applied for the ceritificate on these grounds.

The appeal was disallowed on the grounds that the document certifying permanent residence did not represent permanent residence for the father and that as he was not a qualified person currently, nor done 5 years work according to the facts of the case the client could not derive rights from him.

From the outcome there appears to be discrepencies in EEA nationals claiming permanent residence for immigration purposes and retaining this for benefit purposes, but there is nothing in caselaw or guidelines stating the differences between them or suggestions of whether someone obtaining a document certifying permanent residence may still have to satisfy the right to reside test for benefits??? Presumably when someone has permanent residence they are no longer a person from abroad and so do not have to satisfy the right to reside, unless there is something that I am missing??

Any information is very welcome!!