[Shader] How to use Blend SrcFactor DstFactor, SrcFactorA DstFactorA

I have done lot of searching about how to get it to work since a very long time ago but no matter what factors I put in and what platform or project settings I switched to, I can never seen any difference between using Blend SrcFactor DstFactor, SrcFactorA DstFactorA and Blend SrcFactor DstFactor

the factors in SrcFactorA DstFactorA part is always being ignored.

Can anyone help?

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