First of all thank you for having indicated this document. I admit that the Post Boy sham was not among the documents I have read and it has some interesting particulars while other seems to be a little "guessed".
Referring to the question that started this thread, my opinion is that most of the contents of the cathechisms are compliant to the content of the Legend of the craft. However some of them have been modified according to the changes that have likely happened around the end of the 1600. For example the "Graham" (1726) includes many forced interpretations, so question and answers are likely ancient, but explanations included are recent. However I think that other questions and answers present in other catechisms are not masked at all. In some cases, in facts, even a clear phrase can hide something if you do not know what is behind it. The only problem is that, unfortunately, we have lost a lot of material therefore, even in the best situation, it will be difficult to reconstruct completely how were the rites before 1717.