Streamline;
I flew a few British airplanes when I was a youngun and I was not impressed with their manuals either. I am only talking here about Boeing really, since I am not aware of the Airbus manuals. But from what I have read here I can see that the tendency of airline managers to write procedures themselves exists in Airbus fleets too.
I know that for the latest generation of airplanes Boeing spent a lot of time and money to get the best procedures for their product, and the design of the systems and switches were optimised for those procedures so that everything works as well as it can. They had specialists in time and motion, engineering, flight crew (including trained and qualified test pilots), education, medicine and so on to conference, suggest, test and apply it all. The end result is what we, the greasy end, have to work with.
Yet many airlines don't even bother to try it before they substitute their own procedures. They have no idea what affect this will have on the safe or efficient operation of the airplane, and often are not aware of the damage they do. They justify it by saying it is "standardization", or it is intended to reduce training cost, or simply (usually) it is done because the old codger writing the new procedures does so to make it comfortable to himself.
It goes without saying that the airline managers and their helpers do not have the qualifications of those who designed the original procedures. The pilots accept the way the airline tells them to do it, and most of the time they are not aware of the deficiencies, nor even that what they are doing is not 'standard' (what the manufacturer intended).
If the changes were beneficial, then you can be assured that the manufacturer would pick them up and make them part of their own procedures. This practically does not happen, which should tell you something.
Many of the changes made do result, by themselves and as part of the whole procedure, in a less safe and less efficient way of doing it.
Changing the B744 procedures to agree in part with the 747 Classic, for example, is a terribly short sighted way to do it. But Lufthansa (among others) does exactly this.
The new airplanes are downgraded (dumbed down) for a short term benefit and once the procedures are written, it is extemely hard to change them.
Ansett bought new F27-400s with F27-100 flight instruments, for example, intending to save money on training, and I have heard some airlines have tried to do the same with the newer glass cockpit types (CX for one). This is an extreme example of what I am talking about of course, but even if the change is simply to move the control check to the taxi phase instead of doing it before start, as the manufacturer intended, has adverse affects on safety and cost.
In fact I know of no changes that result in an improvement. Maybe you do?