My understanding is that when the CCRC issue Statements of Reasons, they identify which commissioners have considered a particular case. A commissioner would not be involved in reviewing cases where there is, or could be perceived to be, a conflict of interest.
If a particular commissioner has previously represented Jeremy in some professional capacity, he probably wasn't under any specific obligation to inform Jeremy, it's more about making full disclosure to the CCRC about his work and background and any potential conflicts before accepting the appointment; though I agree it would have been courteous to tell Jeremy if he was still acting for him at the time.