Backdates of Severe Disablement Allowance and Pension Credit (ignored as capital?)

The client affairs team of a local authority manages one of our tenant’s finances and they recently said that he has received a large backdate of SDA. Pages 361/362 of the current CPAG book list the benefits from which the backdated payments are ignored as capital for 52 weeks or more (in cases of official error).

Does anyone know if the same rules apply to SDA? I was also wondering about Pension Credit as it isn’t mentioned in the list. I know that that PC is not usually backdated more than 3 months, but I was thinking there might be exceptions where an official gave incorrect advice about claiming etc.?

Thanks