Please update the excellent guide at https://devzone.nordicsemi.com/b/blog/posts/getting-started-with-nordics-secure-dfu-bootloader for bond forwarding.
Among other happy Nordic users I am encountering insurmountable problems with projects built with NRF_DFU_BLE_REQUIRES_BONDS set NZ, or NRF_DFU_BLE_BUTTONLESS_SUPPORTS_BONDS set NZ, or both, in sdk15.2. Here's hoping the completion of the TBD section in Mr. Hung's excellent guide can cure my woes.