I think the game treating portals as fuzzy holes in reality is more just a limitation or oversight in the physics engine. It completely ignores relativity and makes the portals no longer logically consistent and pointless to argue about. Velocity and angle conservation relative to the portal is established elsewhere though, so running with that gives you the “fly up” result.
But the game treats the portals as holes in reality. If a whole falls on you do you suddenly pop up out of the other side? No.
It would plop. It would only fly up if the platform the cube was on moved up towards the portal.
I think the game treating portals as fuzzy holes in reality is more just a limitation or oversight in the physics engine. It completely ignores relativity and makes the portals no longer logically consistent and pointless to argue about. Velocity and angle conservation relative to the portal is established elsewhere though, so running with that gives you the “fly up” result.