Well, I never placed a note about this in the Hoaxes section, because I figured that everyone saw my post in the Combining section, posted in August of 2000.
Anyway, no particular week gives better stat carryover or better tech carryover.
Yes, each week has a formula making it much more likely that you will get a particular breed from a combo that week, but that's it.
Read my post in the Combining section "Interesting Results From Combining! (Tech Carryover) " for full details!