No the are not part of the fediverse, at the moment, mostly because of the privacy issue described in the faq. I think they are open to it in the future depending on how they solve the issue. But they are not commercial either, so they have no inzentive for ads or other company policies. Raddler is just one part of postmill, just like lemmy.world is one part of the fediverse.
Iv read about Thorium the last 3-4 years and it seems so promising. Im really disapointed that the push is not greater as it would make everything a lot more safe.