For example today's downloads were Benz and Maybach. If you download Benz first you still need to download Maybach even though they are in the same family and same folder in the tool. There is a Maybach folder but just for logo and pointer to Benz folder.
If you download Maybach first, this will include Benz and save you downloading both files. This is the same for Acura/Honda, Lexus/Toyota, Infinity/Nissan, etc.
My MaxiSys download speed is really slow so any time I can save is great, especially for lager files.