Sorry, I misunderstood. So your not going to use the SmartThings hub just SmartThing sensors with your own hub.
Now that I understand what is going on here it looks like things are working the way they should. When a ZigBee device connects to a ZigBee network it will send out a ZDO Cluster 0x0013 device announce, and that is what you are seeing. That is supposed to trigger a discovery process from the hub in where it will send several ZDO packets to the sensor to discover what it is and how to communicate with it. The following is an excerpt from an article I wrote this summer for Nuts and Volts about the ZigBee communications between a device and the SmartThings hub.
ZigBee Network layer communications
The ZigBee Device Objects (ZDO) library is a collection of clusters for sending and receiving ZigBee network layer packets. Sending a ZDO cluster command is very similar to sending a ZCL command but with two small changes. To send a ZDO packet you have to set your profile ID to 0x0000 and your destination endpoint to 0x00. This tells your radio to treat the data packet as a ZDO command. ZDO commands are extremely powerful. They allow you to bind devices together, create groups, check signal strength, read routing tables, and query devices for their capability.
To be properly identified on a ZigBee network our IoT panel meter needs to support at least 3 ZDO commands.
• Device Announce, ZDO Cluster 0x0013 see page 111 of ZDO spec. When a ZigBee device joins a ZigBee network it needs to announce itself. This cluster is broadcasted to all non-sleeping devices on the network letting them know it’s available to receive data. Often a device announce will trigger an identification process from the ZigBee Coordinator (hub).
• Active End Point Response, ZDO Cluster 0x8005 see page 163 of ZDO spec. When the hub receives a device announce packet it will send a ZDO Cluster 0x0005 report active end point request. The IoT panel meter will listen for this request and respond with a list of its active end points by sending a ZDO Active End Point Response packet 0x8005.
• Simple Descriptor Response, ZDO Cluster 0x8004 see page 161 of ZDO spec. Once a list of endpoints has been received by the hub it will then ask for details on each end point by sending a ZDO Cluster 0x0004 report simple descriptor. The IoT panel meter will listen for this request and respond with the details for each end point in a ZDO Cluster 0x8004 formatted packet. This packet will contain a list of clusters supported by that end point.
Your will need to write some firmware for the xBee to send out these packets to communicate with the devices. You have done some good work to get this far hope this helps!