Here is the US version for reference...
https://www.ecfr.gov/current/title-1...A/section-91.3
A paragraph in an operator's OMA or FCOM (stating the obvious) is not a CAR or a CASR.
My company OM, like most I would assume, has a similar paragraph. It goes so far as to say, "believing to be the correct action in the event..." So in following my company manual "accepted" by CASA, do I gain some protection?
Whenever Australian pilots talk about being caned by CASA for a transgression I am reminded of the inability of CASA to find anyone to cane when a Qantas aircraft took off from Hobart without having the runway lights turned on. Then followed up by a Jetstar aircraft at the same airport a few years later.