this is loosely aligned with the old Cat' A
To be clear: Cat-A is an
airworthiness criteria, used in certification of the aircraft. The Cat-A standards include: (1) multi-engine design, in addition to engine/system isolation (which ensures that failure of one item won't result in failure of the remaining systems); (2) OEI performance, which allows for continued safe flight and landing; and (3) scheduled procedures for takeoff and landing (to include WAT limits).
To be PC-1, you must also have Cat-A design ... without this design, there's no way to guarantee that you can "operate the the helicopter in such a way as to ensure that, in the event of the failure of an engine, the helicopter can either continue with flight or carry out a safe landing."
Clear as mud!