It’s not that the points outside the light cone don’t exist. It’s just that each point represents a “spacelike displacement” rather than a “timelike displacemen

It’s not that the points outside the light cone don’t exist. It’s just that each point represents a “spacelike displacement” rather than a “timelike displacement”. If you like, you can think of any point outside the boundary as happening simultaneously to the spacetime point at the vertex of the cone, if you just pick the right reference frame.