Did Japan stoke Chinese rebellions?

Did Japan encourage the uprisings that tied down much of the Chinese army?

Probably not; Japan may have welcomed them, but China's existing internal conflicts already served that purpose without intervention.

Japanese involvement was possible in principle but probably unnecessary. China already had enough internal conflicts to disperse its strongest forces without outside encouragement. The comparison is Germany's attempt to provoke conflict on the United States' southern border during the First World War, which risked stimulating the very mobilization Germany wished to avoid. Japan already received the strategic benefit of Chinese distraction, so covert intervention would add exposure without a clear need.