CBuffer not populating when using SRP Batcher compatible shader

How to reproduce:
1. Open the attached “IN-105427“ project
2. Open Assets/ISS/ReproScene
3. Observe the Game View

Expected result: All quad objects are coloured
Actual result: Quads rendered using SRP-compatible shader are white

Reproducible with: 6000.0.51f1
Could not test with: 2022.1.0a1, 2022.3.63f1, 6000.1.9f1, 6000.2.0b7, 6000.3.0a1 (compilation errors of custom package scripts)

Reproduced on: MacOS 15.3 (M2 Ultra), Windows 11
Not reproduced on: No other environment tested

Notes:

• Building this project is difficult due to many dependencies
• The color is being read per vertex, rather than per fragment (as occurs with regular SRP shaders)
• The quads are rendered via Sprite Renderer, and the project uses Entities
• Easiest to debug by attaching a built Unity Editor and getting a frame capture from the Game View, doing so will show that the color vector in the cbuffer is 4.0980210304