How to reproduce:
1. Open the attached project's Scene labeled "SampleScene"
2. Enter the Play Mode
3. Inspect the Console Window's message
4. Go to Build settings (File->Build Settings)
5. Enable the Development Build option
6. Click "Build And Run"
7. Inspect the Console Window in the Build

Expected result: Scene.IsSubScene returns the same value in the Editor and Build
Actual result: Scene.IsSubScene returns a different result

Reproducible with: 2019.3.2f1, 2020.1.0a23
Couldn't test with: 2017.4.37f1, 2018.4.17f1 (Scene doesn't contain a definition for isSubScene)