In order for the challenge and response to be completely correct, you would need a separate checklist for the bleeds off option, some operators prefer to keep it simple and the "packs set" allows for bleeds either off or on. Airmanship applies in this case, but unfortunately we don't have any checklist items for airmanship. I know that some companies that have a "bleeds off" take off procedure checklist on the reverse side of the normal checklist.
The examiner is quite correct regarding checklist compliance, but blind systemisation can lead to unanticipated errors. It is up to the company to decide whether a separate checklist is needed.