Two players may be standing far enough apart that the best high-precision Unreal origin is different for each of them. Requiring one shared rendering origin would turn a local numerical concern into a global limit.
The server therefore retains durable placement in the celestial hierarchy while each client represents nearby actors relative to its own origin. Rebasing a client changes coordinates, not the actual game-world location.
This immediately creates a discipline: replicated and saved values must identify their frame. A raw client-world vector cannot become durable state merely because it currently points at the correct place.