Godot Engine: Why is baking light making my scene darker?

Apparently I don’t understand real time lighting. I have an interior scene with some windows. The light is from an OmniLight near the ceiling, default environmental light from outside, and a desk lamp with emission. Without baking light, the scene looks like this:

enter image description here

Consistent with the documentation for emission, the desk lamp is not affecting the surrounding objects. I want to bake the light to see the lamp’s effect and to support low end hardware.

I followed the baked lightmaps tutorial and set the BakedLightmap’s extents to encompass the entire room. After baking, the scene looks like this:

enter image description here

I can see the lamp’s light, as expected, but now everything is too dark. It is unclear to me from Godot’s documentation if scenes include indirect light without baking. I have tried this with the OmniLight set to bake "all" and only indirect light.

What am I missing here?