Steps to reproduce:

1. Open the linked project (or set up a project for HDRP usage from https://github.com/Unity-Technologies/ScriptableRenderPipeline)
2. Open 'GammaTest' scene
3. Open Game view or focus one one of the Lit planes, notice how are they too bright
4. Select 'Directional Light' object in hierarchy
5. Notice how both Lit planes are now correctly lit

Notes:
After selecting the Directional Light object, the scene becomes dirty, and if you save it, then after re-opening the planes will be correct. If you don't save the scene, upon re-opening the planes will be incorrectly lit again until selecting DL object.
Same happens on Windows.