My company wrote and printed its own flight manuals and checklists so the same company culture and operating policies would be consistent across the fleet. And, they remained compliant with the O.E.M.'s procedures.
In a light-hearted vain: I heard stories in BEA days that, allegedly, the Trident guys tried to re-wrtie the replacement B737 manuals so their guys, converting across, would understand them. This story came from an airline I flew with who were helping with line training some BA crews in their early days of B732. They were completely bemused as to how you could transfer a 3 man crew philosophy to a 2 man crew a/c. The roles of PF/PNF were swapped about and mingled up. That other airline flew cording to FCTM. Their philosophy was why buy a new toy and change the operating instructions. You don't do t with anything else in your life. OK, it was simplistic, but.......and in a later life, as they modernised, indeed their local XAA wanted full SOP manuals.
I also flew B767 for various outfits. I was taught, first time on type, by a top of the chain training dept. 4 airlines and 15 years later (don't ask) I and a friend ventured into the clutches of fledgling B767 operator. They had B733's. The CP B767 fleet wrote the B767 SOP's My friend & I were flummoxed. Some were so non-sensical. Where had these ideas come from? It turned out the new CP fleet was a biz-jet pilot for the airline boss and ex-B707 pilot. Mystery solved, but what a mess.
Sorry for head drift, but Aperster sucked me into it on a slow night.