Cannot change opacity of area from config

[ZacharyBys]

Bug Description

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "width": 300,
  "height": 200,
  "data": {"url": "data/unemployment-across-industries.json"},
  "mark": {"type": "area" },
  "encoding": {
    "x": {
      "timeUnit": "yearmonth", "field": "date",
      "axis": {"format": "%Y"}
    },
    "y": {
      "aggregate": "sum", "field": "count",
      "title": "count"
    }
  },
  "config": {
    "area": {
        "line": true,
        "opacity": 0.1
    },
    "style": {}
  }
}

Area doesn't consume opacity changes from config, this only works if opacity is set directly in mark