Why would points render in a Highcharts Stock chart when changing range selection?

Question: why would points appear on a Stock chart in Highcharts instead of just plot lines?

I’m playing with the Stock chart module in Highcharts in a Dashboard and I noticed that when I expand or contract the range selection in certain ways then points appear where there were none:

You can try this here: https://jsfiddle.net/zroq19nc/1/

I think I must be missing something when configuring the chart; here’s its component entry in the dashboard:

{
  "renderTo": "stock-cell",
  "type": "Highcharts",
  "chartConstructor": "stockChart",
  "connector": {
    "id": "example-budget-data",
    "columnAssignment": [
      {
        "seriesId": "Total Spend",
        "data": ["d", "Total"]
      }
    ]
  },
  "sync": {
    "highlight": true
  },
  "tooltip": {
    "useHTML": true
  },
  "chartOptions": {
    "chart": {
      "className": "highcharts-stock-chart"
    },
    "title": {
      "text": "Total Spend"
    },
    "series": [
      {
        "name": "Total Spend",
        "id": "total-spend"
      }
    ]
  }
}