Repro steps:
1. Import the attached package and open the repro scene
2. Observe all particles display the number 4 (DX11, DX12).
3. Switch to Vulkan (or be on Metal)
4. Observe the Unlit particles display 5.

Notes:
- Works fine in DX11 and DX12.
- Happens only on Unlit VFX/ShaderGraphs. Works for Lit.
- Works fine on a regular quad, so doesn’t seem like a SG issue, but a SG/VFX integration one.
- Looks like the slice values are either 0 (min) or 4 (max). 0 returns 0, 0 + epsilon returns 4.
- Repro on HDRP. Can't tell if URP is affected due to the 1309219 issue.