Enum field is shown as an Integer field when it is serialized in a nested structure

How to reproduce:
1. Open the “enum_repro.zip“
2. Select the “TestInstance (Test)“ asset
3. Observe the “Enum Variable“ field nested inside “List Of Lists“ in the Inspector

Expected result: An Enum field is seen
Actual result: An Integer field is seen

Reproducible with: 2021.3.29f1, 2022.3.8f1, 2023.1.10f1, 2023.2.0b7, 2023.3.0a2

Reproducible on: Windows 10
Not reproducible on: No other environment tested

Note: See how the “Enum Variable2“ field works correctly (not nested)