Shifting from one world to another in realtime in UE4

Greetings. I was watching a video leak of a cancelled game : Legacy of Kain: Dead Sun the Soul, the Reaver successor (legal leaked content since the devs themselves told people to leak it since it was cancelled). One fo the game devs who worked on it surprised about a fact: it seems UE3 couldn’t handle realtime world shifting very well which is the basis of Soul Reaver universe. Here is what he said : “this was running on 360, so remember that - the creaking you can see was the engine running two entire levels at the same time, so that you could shift realms at any point, something that UE3 really isn’t designed to do.” :

Here is the ful thread that has the video in it:

You can see in the vidoe that the transition from real world to soul world is rather choppy, unnatural, buggy resulting in many artefacts in the scene. I know Square Enix switched to UE4 for Kingdom Hearts III because it can have many different types of shader: Kingdom Hearts 3 dev discusses switch from Luminous to Unreal Engine 4 • and that UE4 is betetr capable of handling the diverse shaders that every switch from one world to another implies. If so, it means Kingdom Hearts III could shift from one world to another with ease unlike UE3 or maybe the worlds’ transition Dead Sun is more complex involving going from one scene to a different other with other geometries , characters, post process etc that both UE3 and UE4 can’t handle, something the Gex engine could handle painlessly at that time ?