Hi. I had to check that modpack by myself.
Looks like the updates were made by zipping the modpack directory right where it's being stored by the launcher so every new version contains the old version (in the cache directory) and that one has the even older version inside...
All the other unnecessary files are also worth mentioning like directories with logs, options.txt and the additional files in the bin directory that simply shouldn't be in there.
The pack size is enormous right now (around 2GB), after removing all the unnecessary files it should be around 300MB.