I agree - but, as I've said, BS7671 is inconsistent with that "reasonable" approach by saying that RCDs are regarded as an acceptable means of "additional protection" only "in AC systems" and, more specifically, restricts the requirement for RCD protection of sockets to only those in "AC systems".That does not seem at all unreasonable to me, AIUI DC is generally more hazardous than ac of the same voltage.
Hence, it would seem that the requirement for RCD protection of buried LV cables (without excluding cables carrying DC LV) is the only case in which BS7671 is "reasonable", it being fairly "unreasonable" in all other cases.
Mind you, this is probably all pretty moot, since I think one would probably struggle (these days) to find a DC LV electrical installations!
Kind Regards, John