TearsInTheRain

Those folders you were talking about are called index(es). Each index is one SKU and that only happen in a multi-SKU image. All of the original Windows 7 discs and downloads are actually multi-SKU but only one SKU can be installed because they have the file ei.cfg (which pre-selects the SKU for you during the setup). You can export one single index of a multi-SKU image and it will look just as you described (no 1, 2, 3... folders). I haven't looked at those August updated images yet but I am assuming that install.wim contains only one index and maybe that will explain why.
Sometimes, you can install Windows to a computer, then install all updates, Sysprep and add everything back to a WIM file but I don't think Microsoft does that very often. I don't think that the August updated ISOs were done this way and I will take a look at those ISOs later to figure out exactly how they did it.

Version 8.16 (3 August 2019): Fixed links for Facebook site and Twitter feed; added announcement for Windows 7 / Office 2010 download days starting in October; added Insider and developer versions up to build 18950; added Windows Admin Center previews up to build 1907; added Office 2019 for Mac builds 16.26 and 16.27.