CloudWatch alarm considers missing data points before alarm creation

I observed that when my cloud watch alarm is configured to treat missing data as breaching. The cloud watch alarm created at time T considers missing data points before T and alarms. Shouldn't cloud watch alarm only considers data points after the alarm's creation time?

In my case, the alarm was deleted and re-created, I don't know if this is a corner case which triggers the behavior that I saw.

Here are the alarm histories:

• 2023-11-11 07:42:49 Alarm "request_data_from_endpoint_Errors_Sum" created
• 2023-11-11 07:43:42 Alarm updated from Insufficient data to In alarm. Details are below. Please notice that it considers the missing data points between 7:33 and 7:42.

{
  "alarmName": "request_data_from_endpoint_Errors_Sum",
  "alarmType": "MetricAlarm",
  "timestamp": "2023-11-11T07:43:42.851Z",
  "historyItemType": "StateUpdate",
  "historySummary": "Alarm updated from INSUFFICIENT_DATA to ALARM",
  "historyData": {
    "version": "1.0",
    "oldState": {
      "stateValue": "INSUFFICIENT_DATA",
      "stateReason": "Unchecked: Initial alarm creation"
    },
    "newState": {
      "stateValue": "ALARM",
      "stateReason": "Threshold Crossed: no datapoints were received for 10 periods and 10 missing datapoints were treated as [Breaching].",
      "stateReasonData": {
        "version": "1.0",
        "queryDate": "2023-11-11T07:43:42.846+0000",
        "statistic": "Sum",
        "period": 60,
        "recentDatapoints": [],
        "threshold": 0,
        "evaluatedDatapoints": [
          {
            "timestamp": "2023-11-11T07:42:00.000+0000"
          },
          {
            "timestamp": "2023-11-11T07:41:00.000+0000"
          },
          {
            "timestamp": "2023-11-11T07:40:00.000+0000"
          },
          {
            "timestamp": "2023-11-11T07:39:00.000+0000"
          },
          {
            "timestamp": "2023-11-11T07:38:00.000+0000"
          },
          {
            "timestamp": "2023-11-11T07:37:00.000+0000"
          },
          {
            "timestamp": "2023-11-11T07:36:00.000+0000"
          },
          {
            "timestamp": "2023-11-11T07:35:00.000+0000"
          },
          {
            "timestamp": "2023-11-11T07:34:00.000+0000"
          },
          {
            "timestamp": "2023-11-11T07:33:00.000+0000"
          }
        ]
      }
    }
  }
}