To reproduce:
1. Open new project.
2. Create Cube in hierarchy.
3. Open "Lighting Settings" window.
4. Uncheck "Auto Generate" and press "Clear Baked Data". (Scene is still as lit as before)
5. Enter Playmode. (Scene becomes darker)

Expected behavior: When "Clear Baked Data" is pressed, Lighting is refreshed.
Actual result: Lighting is refreshed only when enterring Playmode, or building the project.

Workaround:
Enter Play mode, and go back to Edit mode.

Reproducible: 5.4.4p4, 5.5.2p2, 5.6.0f1, 2017.1.0a3