As with all manuals again the question arises:
Do you want to publish the knowledge at all?
Unfortunately we always think to complicated. Why not let the user decide in how deep he wants to dig into. Offer an understandable staged approach to SOPs.
1. Tell the user the essential - kneed to know
2. Tell the user the in depht knowledge - nice to know
3. Tell the user where the source is and give him arguments and reasons why the SOP is the way it is - offer him reason.
In my opininon there is usually too little information. The SOPs are sometimes poorly written, ambigous or not concise. Many companies struggle with procedures which are not thought through. The mor information you make available the better any user can pick what he deems necessary for his understanding.
Apart from this - live the SOPs - develop a philosophy and live it because this is the way people pass that on to the new ones.