If I understand correctly this is direct lighting using ray traced shadows leaking, so not really Lumen.
Most likely it’s due to ray tracing culling removing distant stuff from the BVH. Check out Ray Tracing Performance Guide in Unreal Engine | Unreal Engine 5.5 Documentation | Epic Developer Community to understand how to configure it. You can also use RT (or Lumen) visualizations to see whether BVH contains that Landscape in the distance.
Initially we had RT culling disabled, but people complained about poor RT performance, so now it’s enabled with some reasonable default settings.