Agreed! When discussing the books, one must choose either cover date or release date for comparisons. I also agree with the 3 sections as a more accurate way to break things down.
The other matter of October 1957 ... I used to think exactly what you wrote, until I became aware of another comic: Cartoon Kids #1. I know people have said this and that about Mike's Amazing World of Comics not having completely accurate dates but see what you make of this: Dippy Duck #1 has an October cover date and is listed as being on sale May 13th,1957. Patsy Walker #73 also has an October cover date and is listed as being on sale July 15th, 1957. That all makes sense to what the general consensus is/was. Ok, now here comes Cartoon Kids #1 without a cover date, but WITH an Atlas globe on the cover and an on-sale date of July 1st, 1957, positioned directly between the other two comics. I don't know why it doesn't have a cover date or an indicia date. I was lucky to find a copy for sale on eBay that is helpful in that the auction shows the indicia and the comic has an arrival date stamp of Aug 9, 1957 (see pics below). Based on what little evidence I've been able to find, I think maybe the Cartoon Kids #1 was the last comic to have the Atlas globe. This, by the way, isn't any kind of big deal or anything, just some new information to share and discuss.