Google Smart Home can't recognize "action.devices.commands.TimerStart" command

Question

I'm integrating my sprinkler product with Google Smart Home. Everything works except that the "action.devices.commands.TimerStart" command cannot be recognized by Google smart home.

Below is my SYNC response:

  "body": {
    "requestId": "12486236378229063564",
    "payload": {
      "agentUserId": "Oliver",
      "devices": [
        {
          "id": "AAAA-BBBB-CCCC-DDDD",
          "type": "action.devices.types.SPRINKLER",
          "traits": [
            "action.devices.traits.Timer",
            "action.devices.traits.StartStop"
          ],
          "name": {
            "name": "Front yard"
          },
          "willReportState": true,
          "deviceInfo": {
            "manufacturer": "ABC company",
            "model": "ABC",
            "hwVersion": "3.2",
            "swVersion": "11.4"
          },
          "attributes": {
            "maxTimerLimitSec": 86399
          }
        }
      ]
    }
  }

Below is the QUERY response:

    "body": {
    "requestId": "7683156339707030974",
    "payload": {
      "devices": {
        "AAAA-BBBB-CCCC-DDDD": {
          "status": "SUCCESS",
          "online": true,
          "isRunning": false,
          "timerRemainingSec": -1
        }
      }
    }
  }

When I type or speak "Start Front yard" on Google home app, my backend server receives the following command, which is correct.

      "payload": {
        "commands": [
          {
            "devices": [
              {
                "id": "AAAA-BBBB-CCCC-DDDD"
              }
            ],
            "execution": [
              {
                "command": "action.devices.commands.StartStop",
                "params": {
                  "start": true
                }
              }
            ]
          }
        ]
      }

But when I type or speak "Run Front yard for five minutes" on Google home app, my backend server still receives the same command (action.devices.commands.StartStop) as the above. What I expect to receive is "action.devices.commands.TimerStart" command. Can anyone pls help point out what I'm doing wrong?

I expect to receive the "action.devices.commands.TimerStart" instead of the "action.devices.commands.StartStop" command after typing or speaking "Run Front yard for five minutes" on Google smart home.