How to reproduce:
1. Open the attached “IN-94949 json“ project
2. Open the “SampleScene“ and enter Play Mode
3. Observe the result in the Console Window

Expected result: The top-level list is set to null, which causes an error and prints "NullReferenceException: Object reference not set to an instance of an object" in the Console window
Actual result: The top-level list is initialized as an empty list, “0“ is printed in the Console window

Reproducible with: 2022.3.58f1, 6000.0.40f1, 6000.1.0b8, 6000.2.0a5

Reproducible on: MacOS 15.3 (M4), Windows 11 (by user)
Not reproducible on: No other environments tested

Notes:
- Top-level list in “SomeScript.cs“ component which is applied on “Test“ GameObject behaves differently from what is described in the documentation (https://docs.unity3d.com/6000.2/Documentation/ScriptReference/JsonUtility.FromJson.html): “If the JSON representation is missing any fields, they will be given their default values (i.e., a field of type T will have value default(T) - it will not be given any value specified as a field initializer, as the constructor for the object is not executed during deserialization).” The top-level list is missing from the JSON and does not have an initializer in the code, however it is not set to its default value (null). Instead, it’s automatically initialized as an empty list, allowing operations like ".Count" without throwing a "NullReferenceException"
- Top-level list {{firstLevelUninitialized}} and second-level list {{secondLevelUninitialized}} in component “SomeScripts.cs“ return different outputs in the Console Window even though both even though both have no initializer in the code