SwiftUI Chart Axis Alignment Issue

I am pretty new to SwiftUII and having trouble understanding how the Plottable value works in SwiftUIChart?

I have a simple line chart to show step count.

If I define LineMark's x value without unit i.e. value("Week Day", $0.weekday) then plotted data is aligned with x-axis.

But, if I define LineMark's x value with unit i.e value("Week Day", $0.weekday, unit: .day) the x-axis does not align with the plotted value’s "date". Meaning that the line get plotted from between the first and second x-axis value.Since the first data from the chart's data array has the date as Jul 17, I was under impression that the line should start from x-axis having value Jul 17, instead is doesn't. If I remove unit then, the line start from Jul 17.

struct StepCount: Identifiable {
  let id = UUID()
  let weekday: Date
  let steps: Int
  init(day: String, steps: Int) {
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyyMMdd"
    self.weekday = formatter.date(from: day) ?? Date.distantPast
    self.steps = steps
  }
}


let currentWeek: [StepCount] = [
  StepCount(day: "20220717", steps: 5000),
  StepCount(day: "20220718", steps: 15000),
  StepCount(day: "20220719", steps: 5000),
  StepCount(day: "20220720", steps: 10800),
  StepCount(day: "20220721", steps: 5300),
  StepCount(day: "20220722", steps: 10400),
  StepCount(day: "20220723", steps: 4000)
]

struct LineChart: View {
  var body: some View {
    VStack {
      GroupBox ( "Line Chart - Step Count") {
        Chart {
          ForEach(currentWeek) {
            LineMark(
              x: .value("Week Day", $0.weekday),
              y: .value("Step Count", $0.steps)
            )
          }
        }
        .chartYAxis {
          AxisMarks(position: .leading)
        }
        .chartXAxis {
          AxisMarks(preset: .aligned, values: .stride(by: .day))
        }
      }
    }
  }
}