It does in the following senses:

1. Anonymity is provided as long as there is a single trustworthy member, regardless of how many phony members there are.

2. Denial-of-service resistance is provided even against many Sybils - eventually they will all be kicked out of the group and communication can proceed.

This is in contrast to protocols (e.g. onion routing, Aqua[0]) that only provide their security properties when the adversary doesn't control too much of the system. I think it is a fair claim to make and in particular is clear to people familiar with this area of research.

[0] "Towards Efficient Traffic-analysis Resistant Anonymity Networks" <http://www.mpi-sws.org/~stevens/pubs/sigcomm13.pdf>