Specular property of the Shader Graph is not shown on the Material when the Material Override is enabled

How to reproduce:
1. Open the user-attached project “BIRPSpecular”
2. Open the “Material” Material Asset
3. Observe the configurable fields

Expected result: The Specular property of the Shader Graph can be changed on the Material
Actual result: The Specular property can’t be changed on the Material

Reproducible with: 2021.3.32f1, 2022.3.13f1, 2023.2.0f1, 2023.3.0a14

Reproducible on: Windows 11 Pro
Not reproducible on: No other environment tested