Those screenshots are of a test cube he did in Blender, quickly, and exported to UE using a point light inside at the corner (where it may be overlapping the exterior and causing the shadowing being pulled to the other side, or the blockiness). I experiment, and I read the docs, and no I don’t have a bunch of experience in archviz lighting. But I don’t start with the same suggestion that lighting artifacts are caused by lightmap compression being on and low res lightmaps, or even bad UVs in every post I write to try and help. There’s a number of factors involved in lighting, and in the documentation it is obvious that a number of settings can produce artifacts depending on the lights in the scene and what their settings are.
Check this Eden, in the Lightmass Global Illumination page, it states that two settings control for the shadow penumbra size (which is how the shadow edges transition from sharp to blurry / soft). The shadows in your screenshots are blurry on the one heavy-shadow side, at their edges. Here’s the excerpt from the page:
“In the first image is a Static Directional Light with only static lighting, the penumbra size is the same everywhere. In the second image, Lightmass calculated area shadows whose sharpness is controlled by both the light source size and occluder distance. Notice how the shadow of the pillar is much sharper close to where the pillar meets the ground.”
And screenshots:
It’s not required to have high lightmap resolution with all static / stationary geometry. That is the point of LODs (level of detail) and of having global illumination and ambient occlusion settings. The indirect lighting is stored in the lightmaps, and shadow maps are generated which are used in the various shadow features (distance field shadowing, cascaded shadow maps, ambient occlusion, and volumetric lightmaps). Light Source Size and Occluder Distance are settings in a light (such as directional, which is often used for the skylight or in conjunction with it), and control for the shadow transitions at their edges. It’s used to get soft area shadows, or sharper shadowing that is not predicated entirely on UV lightmap resolution. Not everything in the engine is geared toward ArchViz, and is actually a newer development for Unreal since it started as a game engine decades ago.