When the DefaultRenderingPipeline is enabled, the default values for contrast and exposure are set to 1. The background color of the scene should be the same as when the DefaultRenderingPipeline is disabled.
However, there is an issue: the two are not the same.
Test by changing the code on line 82: enableDefaultRenderingPipeline = true or
enableDefaultRenderingPipeline = false
PG:
When you enable the default rendering pipeline, you must convert the clear color of the scene to linear space: