Reproduction steps:
1. Open the attached “BugRepro” project
2. Open the “Scenes/SampleScene” Scene
3. Select the “BugTest” GO in the Hierarchy window
4. Switch from “Normal” mode to “Debug” mode in the Inspector window
5. Attach the “FieldInitialisationBug” script in the Inspector Window
6. Observe the “Test String” value under the “FieldInitialisationBug” component in the Inspector window
Expected result: The value is set to nothing
Actual result: The value is set to “default value”
Reproducible with: 2021.3.33f1, 2022.3.15f1, 2023.2.3f1, 2023.3.0a17
Reproducible on: Windows 10
Not reproducible on: No other environment tested