syedo
I had always viewed SOPs as an aid to standardising pilot actions in respect of a particular type of aircraft across a range of pilots.
They may also be used by an employer to allow multi-crew operations to be standardised from entering the cockpit to leaving it so that two pilots who may never have flown together before feel completely at home.
The idea of writing an SOP (about any topic or phase of flight) that is optimum for a single piston trainer as well as for a large multi engined airliner strikes me as a little unusual.
JF