Canada and Australia each have only just completed, or are in the process of completing a census. (The one in Australia has been a debacle.) So the book must be based upon the results of the 2011 census in each country. I think NZ had a census in 2013.
As a result, I suspect the data and book SBF refers to is a bit out of date.
A while ago, I managed to download a whole heap of data about JW's from the Australian 2011 and 2006 censuses. I have had a plan to get the data from the 2016 Aust census and produce a comprehensive and up-to-date summary, showing trends. It will be a few months away, because typically, it is a while before the results of a census are released.
I don't have the data with me as I write this, but from memory it not only showed JW's were way less likely to get tertiary education, they also earn far less and have slightly fewer children. They are also getting older than the overall population, and have around the same divorce rate as the general population. In the older age brackets, there are far more women than men.
In a side note, I read an old thread about the Aust census where people were puzzled why there were more JW's listed on the census than publishers listed in the yearbook. The answer is simple. Take out the JW's aged between 1 and 10 and the numbers almost match. (Take out JW's between 1 to 15 and there are too many publishers.)