Not entirely true - there is some crossover between the two sections. For example, there were questions on LARS and DAAIS/DACS in my air law exam. There was also a requirement to at least know what the circuit looked like and what distances final / long final etc would be defined as.
I would at least read and understand the comms section before doing the exam.
Better still - sign up to
www.airquiz.com and do some of the exam questions.
Steve