Ductless Mini Split heat pump not cooling / heating outside of room
Consider the flow of air to be similar to the flow of water (because it is)


You are trying to force air from one room into another through a large open space.  The problem is, you're not actually creating any pressure differential.  The air in your room is being moved around by the unit but not being pressurized.  The unit in your room creates a low pressure point and a high pressure point and the air moves around the room stirring up the air and creating an equalization of temperatures within the room.

So the air in your room is blown towards the door at an extremely low pressure.  The air in your hallway is stationary (for the most part) and at the same pressure as the air in your room.  There's really no force behind the air in your room to dislodge the air in the hall, and the air in the hall also has nowhere to go.

Forced air systems work because they have both air outputs and air returns - the returns serve to carry air needing heating/cooling back but doing so also creates that critical pressure differential needed for air to move from room to room.

Otherwise it's like the picture above  the air sits next to each other, mixing only very slowly.