The reason this issue occurs is because draw calls executed via a render event invocation do not inherit the same state that normal draw calls do.
For example, normal draw calls are split into jobs that each have their own copy of a passContext which is updated to enable various passes like rendering reflections and emissions.
The passContext is updated in the job threads. However, the passContext isn't shared with the draw calls that happen within a render event.

The behavior of the builtin renderer's render events has been around for quite some time and we are hesitant to change it as
it could break many developers who depend on it. I would suggest that the developer consider switching to a scriptable render pipeline where they will have much more control over the rendering.

I was able to improve the situation by changing a few things in their project however it does not render identically to the version with command buffers.

They will need to ensure the correct stencil buffer settings are used in "Instanced/InstancedSurfaceShader" by adding the following
Stencil
{
Ref 192
Comp Always
Pass Replace
}

Additionally, they will need to add the following to ensure that reflections are applied to their command buffer draw calls.
cam.AddCommandBuffer(CameraEvent.AfterReflections, gbufferCommandBuffer);

Broken port is duplicate of https://jira.unity3d.com/browse/UUM-3008