Shader warnings are thrown when Initialising Converters in Render Pipeline Converter

Reproduction steps:
1. Create a new project
2. Open Render Pipeline Converter window (Window > Rendering > Render Pipeline Converter)
3. Enable Shaders Converter and press “Initialize Converters” button
4. Observe Console window

Actual result: "Shader 'Mobile/Bumped Specular (1 Directional Light)' not found for upgrader StandardSimpleLightingUpgrader..." warnings are thrown in the Console
Expected result: No warnings or errors are thrown

Reproducible with: 6000.4.0a1
Couldn’t reproduce with: 2021.3.56f1, 2022.3.67f1 (No Render Pipeline Converter window), 6000.0.58f1, 6000.2.6f1, 6000.3.0b3 (No Shaders Converter)

Reproduced on: macOS Sequoia 15.4 (M4)

Note: Full warnings:

Shader 'Mobile/Bumped Specular (1 Directional Light)' not found for upgrader StandardSimpleLightingUpgrader. This may indicate that the shader has been removed or renamed. UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&) (at /Users/bokken/build/output/unity/unity/Modules/IMGUI/GUIUtility.cs:224) 

Shader 'Particles/VertexLit Blended' not found for upgrader ParticleUpgrader. This may indicate that the shader has been removed or renamed. UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&) (at /Users/bokken/build/output/unity/unity/Modules/IMGUI/GUIUtility.cs:224)