It looks like there is an issue in QLog because it sets Netrig's capabilities based on a condition: (caps->has_get_level) & (RIG_LEVEL_RFPOWER) and the default value of caps->has_get_level is NONE for Netrig. As a result, QLog disables the Power Reading.
But it seems I implemented this incorrectly because Netrig's caps->has_get_level gets a valid value after connecting to the rig when rig capabilities are known. It means that QLog should not reflect caps->has_get_level value when Nerig is set in QLog's Settings dialog.