Reproduction steps:
1. Open the submitted project
2. Select TextureImporter Asset in the Project window
3. Select a platform and click override settings
4. Change import settings for that platform
5. Click anywhere in the Editor to deselect TextureImporter
6. Select TextureImporter again

Expected result: Changes in settings are saved
Actual result: Changes in settings are reverted

Reproduces on: 2019.3.4f1, 2020.1.0b1, 2020.2.0a2

Notes:
The issue does not reproduce with Asset Import Pipeline v1.