Hi Yuan Dao,
As you know the The Network Header is encrypted in AES128-ECB mode, using a Header
Encryption Key, derived from the Network Key and The Data Payload is encrypted in AES128-CCM.
So, you will be able to see some data using the BLE Sniffer, but you can't understand this data.
Note: As you know, this BLE Mesh custom example, it is not BLE Mesh Standard. We are not currently supporting BLE Mesh.