Availability of FMG Initialization

Why is the Full Multigrid initialization (FMG initialization) not available? What are preconditions for FMG initialization?

The FMG initialization method is available in the text user interface (TUI) under '/solve/initialize', if a “normal” initialization (either default Hybrid or Standard) has been carried out and if no Multiphase Model is active.

FMG initialization is not compatible with multiphase flows (Volume of Fluid, Mixture or Eularian Model).