You're right about the rationale for the ~4 week rule of thumb differing between various sources. The implementation seems to vary quite a bit too. Matveyev's concept involved wave-like periodization; whereas Verkhoshansky's approach involves more abrupt "blocks" (Viru and Zatsiorsky both support the latter method as well, at least for advanced athletes).
That's an oversimplification, but it's interesting that a monthly structure shows up in these different systems. There is plenty of disagreementon other issuesbetween some of these folks.
Other than AtkoViru's ideas on training effect involution, much of the evidence for this guideline seems to be empirical. Or at the very least, it's not thoroughly documented in the literature that's available in English. Hopefully some members of the group can share additional insights here.
In any case - empiricism is the proving ground where so many lines of study (and eventual principles) are generated. Some things just seem to work better than others. The challenge is to figure out why and how.
You bring up many other great points as well. The notion of coinciding training loads with biological cycles is particularly interesting. In my experience, I had to make some compromises by back-engineering the cycles from one or more target date(s) a team needed to be prepared for. It is rarely a simple problem!
Excelsior Sports •Shelton CT (USA)
Prepare To Be A Champion!