Simple, seedboxes tend to be close to other seedboxes. They then potentially talk to each other over the same network, or a nearby one they peer with, meaning b

Simple, seedboxes tend to be close to other seedboxes. They then potentially talk to each other over the same network, or a nearby one they peer with, meaning bits generally have less distance to travel and over bigger pipes. A disproportionately large number of seedboxes are hosted on OVH's network. The capacity from the seedboxes back to you might not be that great, but it doesn't matter because your home connection is so slow in comparison that it can still easily be saturated.