My experience, Hugh (B737, A319/320/321), is that items like Anti-ice have a checklist response which may be written as AS REQD but which must always be responded to in the specific, i.e. ON or OFF.
AS REQD is not an acceptable verbal response to a checklist challenge, but OK for checklist annotation.
You could always expand further on the range of responses considered acceptable in the Pt B/Aircrew Manual/POH etc.