I’m not aware of any such software limitation.
True neutrals and the Dutch are hostile to the Axis and must be attacked, therefore can’t be moved into on non combat move.
@Pac:
Where Units Can Move
Land Units: A land unit can move into any friendly or friendly
neutral territory,…
Sea Units: A sea unit can move through any friendly sea
zone. It can’t move into or through a hostile sea zone.
@Pac:
Japan may attack Dutch territories
only if a state of war exists between it and the United Kingdom and ANZAC.
Does that clarify it for you?