They say tap washers and electrical outlets in your home should only be fitted by qualified tradesmen too but it's not like either are overly difficult to do.
Ok I just looked at the website and that Enerdrive being any easier to install than other brands is pure sales pitch.
Look at the number of components very few isolators come with more components.
The idea of cutting factory wiring and not breaking warranty is sales pitch too, I don't remember any reason to cut into factory wiring with any of the systems I've used, earth goes to earth, positive from the main and positive to the aux.
Also a 26 step users guide is not something I would consider the easy option given how simple these things are to install.
At the end of the day whether you choose redarc, Enerdrive, projecta or any other brand name they are all equally easy to install and do pretty much the same job the biggest variance is in the price.