That's it in a nutshell for me. With the proviso that as long as you have the knowledge (or the professionalism to want and gain the knowledge) as to why what you're fitting isn't strictly necessary then it's OK.
A similar situation IMHO to the "it must be RCD protected, and if it is all's well in the world". I've been to quote on a couple of jobs in the last few weeks where the customer has been told "It must have an RCD" or "You need a new CU" when neither is true. I just can't make up my mind if it's an excess of greed, or a shortage of knowledge driving them to tell customers such things.