Hi Will,
I didn't see that you had posted while I was writing my last post. I guess that is what many discussions come down to, what exactly is defined by the terms being used.
Whenever I have ever read about or talked to anyone who uses square rule, it is usually in the context of layout from the reference face, whether that reference face is a snapped line or the physical edge of a timber. To clarify, would you then define the layout methodology of the East as square rule, but with a snapped line reference rather than a reference face? It seems to me that the methodology is different enough to merit it's own designation to keep discussion clear.

Is it the use of housings that qualify in your mind, a system as falling under the definition of square rule? I am by no means an expert, and perhaps others can provide more historical context, but it is not possible to have a discussion unless the terms are clearly defined and agreed upon.

http://forums.tfguild.net/ubbthreads.php?ubb=showflat&Number=27400&page=all

The above thread seems to shed some light on the situation. It seems that a critical differentiation is the position of the snapped lines. A centered snap line is a whole separate methodology than the offset snapped lines used in hewing.