The reason electrical contractors (electricians) have to follow instructions as you put it, is because the majority of commercial contracts will have contractual specifications attached to the contract. They have to be followed it's as simple as that!! they tend to be of a higher standard than those required by BS7671, there are also many other standards that they must know and follow....
Do industrial/commercial qualified electricians have a greater knowledge than Domestic electricians, you bet they do!! They work with and on just about everything, from ELV systems to LV/MV Switchboards which will encompasses all of the various Building Services you will find in a commercial building/project of any size. Do they know how to conduct ALL the relevant testing to all these systems and installations, ....most will know more about testing than a domestic electrician and will be using test equipment that domestic electricians will have never seen or heard of, let alone know how, or even where to use them...
Industrial electricians have to maintain factory plant as well as install electrical installations, most of that factory plant will be far outside the knowledge of a domestic electrician. They will be working with 3 phase supplies in all it's guises, sophisticated motors controls, relay and PLC controls, etc etc... Let's put it this way, an industrial electrician will with a little instruction be more than able to say wire/rewire any domestic properties installation, but a domestic electrician wouldn't be able to take the role of an industrial electrician without some very intensive training and instruction, and that's a fact!!!
You seem to be have a very narrow or limited knowledge of commercial work, it doesn't revolve around pulling SWA cables, it encompasses the whole 9 yards of electricians work. Electricians don't do much on the design side of things, (but don't run away with the idea that they can't) that's done by Consultant Electrical Engineers, and supervised by site electrical RE's. Do you honestly believe that a qualified electrician would be capable of designing the complete installation of a commercial project of any size??