To Reproduce:

1. Open the project attached to the post.

2. Goto 'Bundle Builder' in menubar.

3. In the opened editor window select empty_scene in the object picker, set bundleCount to something over 2 & click Build Bundles.

4. Unty builds several StreamedSceneAssetBundles, each of them containing an empty scene, with no scripts in it, despite that all the scripts in the project are recompiled every time BuildPipeline.BuildStreamedSceneAssetBundle is called.

5. If possible Unity would not force recompile scripts if they were not changed when building SceneAssetBundles.

Scripts are not recompiled when building AssetBundles, even if those asset bundles contain scripts or objects with scripts. But BuildPipeline.BuildPlayer also recompiles all the scripts.