understanding input/output clusters in EZ mode and end-device binding

I am new to z-stack and digging through the sample application, and try to understand how things work. right now, I am reading the temperature sensor, thermostat, and heating/cooling unit sample application in the z-stack Home 1.2. I am a little confused about how the input/out clusters are defined in the binding process using EZ mode and end-devince binding request. 

In the sample temp sensor app, the code for end device binding is as follows:

// NOT ZCL_EZMODE, Use EndDeviceBind
static cId_t bindingOutClusters[] =
{
  ZCL_CLUSTER_ID_MS_TEMPERATURE_MEASUREMENT
};
#define ZCLSAMPLETEMPERATURESENSOR_BINDINGLIST        1

// Initiate an End Device Bind Request, this bind request will only use a cluster list that is important to binding.
ZDP_EndDeviceBindReq( &dstAddr, NLME_GetShortAddr(), SAMPLETEMPERATURESENSOR_ENDPOINT,
ZCL_HA_PROFILE_ID, 0, NULL, ZCLSAMPLETEMPERATURESENSOR_BINDINGLIST, bindingOutClusters,FALSE );

And for EZ mode binding, the following is used:

      static uint16 clusterIDs[] = { ZCL_CLUSTER_ID_MS_TEMPERATURE_MEASUREMENT };   // only bind on the Temperature Measurement cluster

      // Invoke EZ-Mode
      ezModeData.endpoint = SAMPLETEMPERATURESENSOR_ENDPOINT; // endpoint on which to invoke EZ-Mode
      if ( ( zclSampleTemperatureSensor_NwkState == DEV_ZB_COORD ) ||
           ( zclSampleTemperatureSensor_NwkState == DEV_ROUTER )   ||
           ( zclSampleTemperatureSensor_NwkState == DEV_END_DEVICE ) )
      {
        ezModeData.onNetwork = TRUE;      // node is already on the network
      }
      else
      {
        ezModeData.onNetwork = FALSE;     // node is not yet on the network
      }
      ezModeData.initiator = TRUE;        // Temperature Sensor is an initiator
      ezModeData.numActiveInClusters = 1;
      ezModeData.pActiveInClusterIDs = clusterIDs;
      ezModeData.numActiveOutClusters = 0;   // active output cluster
      ezModeData.pActiveOutClusterIDs = NULL;
      zcl_InvokeEZMode( &ezModeData );

In the simpledescriptor, the following is defined:

#define ZCLSAMPLETEMPERATURESENSOR_MAX_INCLUSTERS       3
const cId_t zclSampleTemperatureSensor_InClusterList[ZCLSAMPLETEMPERATURESENSOR_MAX_INCLUSTERS] =
{
  ZCL_CLUSTER_ID_GEN_BASIC,
  ZCL_CLUSTER_ID_GEN_IDENTIFY,
  ZCL_CLUSTER_ID_MS_TEMPERATURE_MEASUREMENT
};

#define ZCLSAMPLETEMPERATURESENSOR_MAX_OUTCLUSTERS       1
const cId_t zclSampleTemperatureSensor_OutClusterList[ZCLSAMPLETEMPERATURESENSOR_MAX_OUTCLUSTERS] =
{
  ZCL_CLUSTER_ID_GEN_IDENTIFY
};

For the thermostat, the following is defined:

#define ZCLSAMPLETHERMOSTAT_MAX_INCLUSTERS       3
const cId_t zclSampleThermostat_InClusterList[ZCLSAMPLETHERMOSTAT_MAX_INCLUSTERS] =
{
  ZCL_CLUSTER_ID_GEN_BASIC,
  ZCL_CLUSTER_ID_GEN_IDENTIFY,
  ZCL_CLUSTER_ID_HVAC_THERMOSTAT
};

#define ZCLSAMPLETHERMOSTAT_MAX_OUTCLUSTERS       1
const cId_t zclSampleThermostat_OutClusterList[ZCLSAMPLETHERMOSTAT_MAX_OUTCLUSTERS] =
{
  ZCL_CLUSTER_ID_MS_TEMPERATURE_MEASUREMENT
};

// NOT ZCL_EZMODE, Use EndDeviceBind
static cId_t bindingOutClusters[] =
{
  ZCL_CLUSTER_ID_HVAC_THERMOSTAT
};
#define ZCLSAMPLETHERMOSTAT_BINDINGLIST_OUT     1

static cId_t bindingInClusters[] =
{
  ZCL_CLUSTER_ID_HVAC_THERMOSTAT,
  ZCL_CLUSTER_ID_MS_TEMPERATURE_MEASUREMENT
};
#define ZCLSAMPLETHERMOSTAT_BINDINGLIST_IN      2

ZDP_EndDeviceBindReq( &dstAddr, NLME_GetShortAddr(),
                            SAMPLETHERMOSTAT_ENDPOINT,
                            ZCL_HA_PROFILE_ID,
                            ZCLSAMPLETHERMOSTAT_BINDINGLIST_IN, bindingInClusters,
                            ZCLSAMPLETHERMOSTAT_BINDINGLIST_OUT, bindingOutClusters,
                            TRUE );

//invoke EZ mode
      zclEZMode_InvokeData_t ezModeData;
      static uint16 clusterIDs[] = { ZCL_CLUSTER_ID_HVAC_THERMOSTAT };   // only bind on the Thermostat cluster

      // Invoke EZ-Mode
      ezModeData.endpoint = SAMPLETHERMOSTAT_ENDPOINT; // endpoint on which to invoke EZ-Mode
      if ( ( zclSampleThermostat_NwkState == DEV_ZB_COORD ) ||
           ( zclSampleThermostat_NwkState == DEV_ROUTER )   ||
           ( zclSampleThermostat_NwkState == DEV_END_DEVICE ) )
      {
        ezModeData.onNetwork = TRUE;      // node is already on the network
      }
      else
      {
        ezModeData.onNetwork = FALSE;     // node is not yet on the network
      }
      ezModeData.initiator = TRUE;        // Thermostat is an initiator
      ezModeData.numActiveInClusters = 0;
      ezModeData.pActiveInClusterIDs = NULL;
      ezModeData.numActiveOutClusters = 1;   // active output cluster
      ezModeData.pActiveOutClusterIDs = clusterIDs;
      zcl_InvokeEZMode( &ezModeData );

Here are my questions:

1. doc says to use EZ mode bind thermostat and temp sensor, but they are both initiators, shouldn't we bind a initiator and a target?
2. in the sample temp sensor app, the ZCL_CLUSTER_ID_MS_TEMPERATURE_MEASUREMENT is in the output clusters for end-device binding, and in the input clusters list for EZ mode binding. Why is this? 
3. say we are binding thermostat and temp sensor, and they indeed can be paired. I suppose this works by matching ZCL_CLUSTER_ID_MS_TEMPERATURE_MEASUREMENT, in the input of temp sensor, and output in the thermostat. I can sort of understand how the ED binding works, but cannot seem to have a clue how it works in the EZ mode. 

Thanks a lot for your help on my lengthy question.