I understand your point, but most people would still download from F95 mirrors.I assume you're referencing our process of doing our own archive compressions.
Re-zipping allows us to use better compression methods and gives us smaller archive files.
We do this for two reasons:
1. Smaller files are quicker to download for users.
2. Smaller files means we can have more files on the servers we use to seed these torrents. The space we save with file compressing a singular title might not be significant, but it becomes so when we're hosting over 16,000 titles.
Additionally, having our files compressed doesn't stop them from being seeded. You just extract the archive to your preferred directory, play it there, and your client will keep on seeding the archived file.
It would easier for people to download files from said mirrors and seed them instead.
For example, SamuraiVandalism is split into 3 parts. It is better to make a torrent of the same 3 files so user can just download 1 part and seed it while downloading the 2 others though P2P.
You repacking the files doesn't save that much space, it would be better to use whatever compression your server file system (maybe ZFS?) support.