I meant did you press the transfer button/soft key on the phone, or did you dial the FreePBX transfer code/used a soft key configured to do that.
The phone isn’t really involved in the latter case, but in the former case, the way that SIP works is that the phone starts a separate call to the destination, as though it were a new call. None of the SIP phones I’ve used have sent remote party ID information for the associated incoming call. Only when the attended transfer is completed does a SIP phone tell the PBX that the incoming and outgoing calls are related.
There is more on this topic, with a different SIP phone, at Caller ID with Attended vs Unattended Transfers