thurrott[.]com/windows/windows-10/243391/tip-download-any-version-of-windows-10
gist.github[.]com/AveYo/c74dc774a8fb81a332b5d65613187b15
The article has a link to the .bat [Batch or script] file on GitHub [2nd link above] -- it just shows the text file's content in Firefox when I click the RAW button on the web page, and it can be saved as a .bat file. Download the Media Creation Tool from Microsoft's site, & put it in the same folder as the .bat file. Open a command prompt window -- right click the Start Menu, or in the Start Menu under Windows System, or Run or Search cmd -- type the name of the .bat file and press Enter. This gives you a window where you select the version you're after, and then runs the Media Creation Tool for whichever version you selected.
If you run the Media Creation Tool on its own you'll get the latest version of Win10 available -- this .bat file just lets you download a version that's older. Why? With the problems that surfaced after the last version rolled out, holding off installing it could have made good sense, but if you needed to (re) install Win10, there would have been almost no way to download that prior version. Or, if a version update/upgrade trashes your copy of Win10, and you need to reinstall, you most likely Don't want to install the version that created your problem in the first place. There are probably other reasons I can't think of at the moment.