I have seen and used ‘reference’ or ‘best practice’ documents for tasks that can benefit from better approaches than the ‘mandated’ ones. These were never used for direct production or critical direct production support tasks such as maintenance or inventory control or material handling and storage etc. These activities involved expert subject matter expertise and judgment. Mostly statistical practices, problem solving, graphing techniques, experimental design, data analysis, etc. These activities typically were difficult to determine the conditions under which a specific approach was required or at least the best/most efficient. Training and guidance from true experts was utilized.
I have also seen ‘one signature’ documents used for things that are changed often as new situations occur and new knowledge is acquired - mostly for Customer support personnel. for example diagnostic trees…
It would be helpful if hte OP could explain their situation and why they want the instruction to be mandatory…