Difference between Sensor.SensorData.accelerometerData and SensorInfo (info.accel)

Hello! I'm trying to get the accelerometer's data in Garmin connect iq application.

This is the my initialize() function that register DataListener and the callback function.

function initialize() {
    View.initialize();

    var options = {
        :period => 1,
        :accelerometer => {
            :enabled => true,
            :sampleRate => 25   // maximum 25Hz
        },
        :heartBeatIntervals => {
            :enabled => true
        }
    };

    try{
        Sensor.registerSensorDataListener(method(:accelCallback), options);
    } catch(e) {
        System.println(e.getErrorMessage());
    }
}

And I found this two. But I don't know what to use and the difference between them.

1. Sensor.SensorData.accelerometerData

function accelCallback(sensorData as Sensor.SensorData) as Void {
    var view3 = View.findDrawableById("Listen") as Text;
    view3.setText(Lang.format("$1$", [sensorData.accelerometerData.x[0].format("%d")]));
}

2. Sensor Info

var info = Sensor.getInfo();

if (info has :accel and info.accel != null) {
    System.println(info.accel);  // [x, y, z]
}

Also, both worked well when I tried to run on a simulator (computer).

But on my real watch(Forerunner 55), the first one does not work. `info has :accel` returns "true" but it is "null".