Reproduction steps:
1. Open the attached "ASD" Project
2. Open the "Assets/Test Lit Shader Graph.shadergraph" Shader Graph
3. Observe the Console Window

Expected result: No error is thrown
Actual result: "Shader error in 'Master': redefinition of '_SpecColor' at line 294 (on metal)" errors are thrown in the Console Window

Reproducible with: 12.0.0 (2021.2.0b1), 12.1.10 (2021.3.22f1), 14.0.6 (2022.2.13f1), 15.0.4 (2023.1.0b10), 16.0.0 (2023.2.0a8)
Not reproducible with: 10.10.1 (2020.3.46f1)
Could not test with: 11.0.0 (2021.2.0a2 ((Cannot find the code for this Target, a package may be missing.)), Editor versions lower than 2021.2.0b1 (Graph Built-In Target is Unknown)

Reproducible on: Intel MacOS 13.2.1

Note: For reproduction to occur, the Specular Color type Property has to have "Reference" set to "_SpecColor" and be connected to the Fragment Node