The problem is that there is general confusion regarding SOPs / Flows and checklists.
A simple example;
Most schools will have a section of their extensive list what they call a "Shutdown Checklist".
This "Checklist" can have 20 items and the pilot is sitting there with the engine running and reading how to shut down the aircraft from a list.
Once they think that they have completed the list they get out and walk away.
The problem is that they have not checked that the list was done. It is entirely possible that they forgot to take the keys uot and the mags are still "live"!!!
In something like a C172, the shoutdown checklist could be;
1. Mags Off
2. Master Off
(Stands back and waits for the "You don't shut down the engine using the Mags")
I know that and by producing the above checklist I have not said how to shut the aircraft down....that is a procedure that should be learned. What the simple two point checklist above ensures is that the main killer items - the mags and master are off so you won't flatten the battery and have not left the mags on.
Looking at the Pre-landing checklist - what do you really need to check in a C172 other than that the fuel selector is on Both and everyone secure - therefore it is another 2 item checklist.
The flow that one does prior to joining final approach - Brakes, Carb Heat, Seats and Seatbelts etc etc etc etc etc etc etc etc etc is something different and can have lots of items. But it is not a checklist - it is a procedure via which one configures the aircraft for final approach.
You could even add "touch-up the lippy in that little mirror" to the procedure but does that have to be in the checklist? Is it a killer item? What is the big problem if it is not done prior to landing?