Good observation, but I just want to point out that the full dumps are downloaded from different servers. They are even mirrored by other institutions. See https://meta.wikimedia.org/wiki/Mirroring_Wikimedia_project_...
However it suffers the number one torrent issue: they do not tolerate change. This means that
- When an article changes, you need to generate a new torrent - When a new torrent describes the archive, it needs to be downloaded from scratch by all peers, so that the maximum number of peers are available for a newcomer.
I hope you'll understand that this is not the official way to distribute archives...