Culling inverted

I am trying to fill a render texture (rt) with a material. My assumption was that using RenderingUtils.fullscreenMesh as the mesh and identity matrices for MVP should take care of that. Well, it almost does - except apparently the culling order is inverted. The code below will not render due to backface culling.

When I insert a cmd.SetInvertCulling(true) call everything works. But why is that necessary?

    void OnEnable()
    {
        RenderPipelineManager.beginFrameRendering += OnFrameRendering;
    }
    void OnDisable()
    {
        RenderPipelineManager.beginFrameRendering -= OnFrameRendering;
    }

    private void OnFrameRendering(ScriptableRenderContext rc, Camera[] cameras)
    {
        var cmd = new CommandBuffer();
        cmd.SetRenderTarget(rt);
        RenderingUtils.SetViewAndProjectionMatrices(cmd, Matrix4x4.identity, Matrix4x4.identity, false);
        cmd.DrawMesh(RenderingUtils.fullscreenMesh, Matrix4x4.identity, mat, 0, mat.FindPass("Forward"));
        rc.ExecuteCommandBuffer(cmd);
        cmd.Clear();
    }

Looks like Unity flips everything upside down and then inverts culling to compensate for it when rendering to an RT instead of a framebuffer. Weird.