In one of his most memorable speeches, Gwok Jing made this distinction to Kublai Khan: he (Gwok Jing) would shed his blood to defend his Han kinsmen, not the corrupt Sung Dynasty that ruled them.
This leads me to think: Gwok Jing never rebelled against the Sung government in LOCH or ROCH because the nation was under assault first by the Jurchen and then the Mongols and could not afford internal chaos on top of external invasion. Had the Sung Kingdom not been imminently threatened by foreign invaders, however, would Gwok Jing have willingly joined a rebellion against the Sung Dynasty government if the rebel forces had the goal of instituting a better native regime?