VA obviously planned on both routes being serviced hence the extra crew. Now that the Hong Kong flights have been cancelled, the extra crew are surplus to requirements. Hence discussion of taking annual leave, long service leave and LWOP. It's probably a prudent approach over the short term as the medium to long term options are not that great if the virus fears continue and new routes for the 330 are not found. The 330 crews have an added dilemma of recently being covered by the wide body EBA which means they have limited options of being assimilated back into the B737 ranks as the narrow body EBA protects existing narrow body pilots from being displaced from existing roles.
Also, VA may be expecting the new Haneda service to be adversely impacted by the virus as well.