Reading https://yggdrasil-network.github.io/about.html it's even more unclear. They claim to have invented something much better than traditional routing but there is no mention of how Yggdrasing perform bandwidth/latency/cost-aware routing.
If you are interested, I suggest you stop by on the matrix room and chat about the different topics. Its rather large and I'm not a developer on the project, just someone learning from those better than me. Mostly in that room.
#yggdrasil:matrix.org