GI, global illumination, is produced by dynamic lighting via ray tracing. The volumetric lightmap is another aspect that remains in dynamic lighting which uses interpolated light data from Lightmass and/or the built-in lighting system of Unreal Engine. To say dynamic lights don’t produce GI is a generalization. The skylight itself can be set to movable, and fills the whole scene with diffuse lighting, and the directional light is similar yet has more fine-tuning properties for other purposes. Unreal Engine is not merely an ArchViz engine. It’s also a game engine, and is utilized for other types of scenes that require dynamic lighting. So using dynamic lighting is not in and of itself wrong. The main concern is performance, as it’s stated to have a larger impact in memory use and processing time.