Hi. The original intent of the deviceid property in the XLSForm specification was to help you retrieve the Mobile Equipment Identity (IMEI) number that is associated with a mobile phone. This number is unique to every phone. For different reasons, this property does not exist or has been hidden in some operating systems. For this reason, the implementation of deviceid in Survey123 does not actually retrieve the IMEI number. Instead, it retrieves a unique string that identifies a installation of Survey123 in your device. When Survey123 is installed, the unique string is created. The deviceid property retrieved from Survey123 will be the same for a device until you reinstall Survey123.
In your particular case, it looks like you want to automatically keep track of the person that is submitting records from Survey123. Since the deviceid string will change over time when Survey123 is installed, I am afraid that the method described will not be robust. Your pulldata table will change over time.
I think a most robust approach is to provide an ArcGIS Account to people using Survey123. Survey123 uses editor tracking to tag every record submitted with information about the time when the record was added or updated. Editor tracking also automatically keeps track of the name that makes the add or update.
