This sounds funky.
Usually sovereign citizens are extreme "leave me alone" libertarians with delusions about the feds respecting magic incantations involving maritime law and garbage like that...people who can't grasp that the feds are limited only by the people's willingness to push back in strong enough numbers.
This is so different from their usual M.O. that it almost seems like a false flag of sorts. That said, the thing about delusional lone wolves is that they can come to believe basically anything in their isolation.
EDIT: Ahhh...after reading more, it's clear these are a completely different kettle of fish, who are being called the same thing for whatever reason...probably not a good reason. Sooner or later, all of the "will not comply" people may be labeled "sovereign citizens" too.