"Customized in source" option to set background color for Single Value does not work

[Zhongtan]

I tried to use "customized in source" option in Splunk Cloud (9.1.2312.203) Dashboard Studio to create a Single Value which background color is controlled by search result.

However the code does not work.  The same code below is tested with statics option which works well.

Below is Dashboard JSON

{
    "visualizations": {
        "viz_74mllhEE": {
            "type": "splunk.singlevalue",
            "options": {
                "majorValue": "> sparklineValues | lastPoint()",
                "trendValue": "> sparklineValues | delta(-2)",
                "sparklineValues": "> primary | seriesByName('background_color')",
                "sparklineDisplay": "off",
                "trendDisplay": "off",
                "majorColor": "#0877a6",
                "backgroundColor": "> primary | seriesByName('background_color')"
            },
            "dataSources": {
                "primary": "ds_00saKHxb"
            }
        }
    },
    "dataSources": {
        "ds_00saKHxb": {
            "type": "ds.search",
            "options": {
                "query": "| makeresults \n| eval background_color=\"#53a051\"\n"
            },
            "name": "Search_1"
        }
    },
    "defaults": {
        "dataSources": {
            "ds.search": {
                "options": {
                    "queryParameters": {
                        "latest": "$global_time.latest$",
                        "earliest": "$global_time.earliest$"
                    }
                }
            }
        }
    },
    "inputs": {
        "input_global_trp": {
            "type": "input.timerange",
            "options": {
                "token": "global_time",
                "defaultValue": "-24h@h,now"
            },
            "title": "Global Time Range"
        }
    },
    "layout": {
        "type": "absolute",
        "options": {
            "width": 1440,
            "height": 960,
            "display": "auto"
        },
        "structure": [
            {
                "item": "viz_74mllhEE",
                "type": "block",
                "position": {
                    "x": 0,
                    "y": 0,
                    "w": 250,
                    "h": 250
                }
            }
        ],
        "globalInputs": [
            "input_global_trp"
        ]
    },
    "description": "",
    "title": "ztli_test"
}