I have that book, but I would be leery of considering it authoritative on anything. As I've mentioned before, even the title is wrong: the Naval reserve was first created in 1923. So they are 13 years off.
That's OK since it is not meant as a history textbook but rather as a book of stories. Thus they try to be polite.
I can't see why the regulars of WWII would have wanted to refer to reservist as such. They were already disparaged as the "wavy-navy", for one thing, and its hard after all for 10% of a force to think its shadow is 9 times bigger. That's about the reg/res proportions during the war : 90% reserve and 10% regs. And how would they distinguish between the RCNR (professional mariners enrolled for the duration that were probably as good - if not better - seaman than the regs) and the RCNVR, the real volunteers?