Boeing logic, at least on B744, is that it wants to reach a new altitude in 2 minutes.
So a climb of 2000' in FLCH ot VNAV will give you a ROC of 1000'.
If you are cleared to climb for example 10.000', it will still want to reach the new level in 2 minutes time, and will go to THR REF. , max. Reference thrust as computed by the FMC.
So for small altitude changes, V/S is never needed, the aircraft will give a sensible climb rate anyhow.