Does the SSPV believes it is The Church?
Are the SSPV self-professed sedes (sedevecantists)?
SSPV, CMRI, and those associated with the late Bp. Dolan are sedevacantists.
RCI (which is headed by Bishop Donald Sanborn) and some other foreign apostolates like IMBC from Italy are sedeprivationists (which posit that the Vatican 2 pontiffs were duly-elected with legal title to the Papacy, yet did not formally attain to actual authority or jurisdiction due to their own impediments).
Either way, a long interregnum, although mysterious, is preferable to a Church that formally teaches error or introduces poison to her flock.