That's expected as the partition is empty since they are loading it from userspace.
You can get the FW from stock FW and wrap it with their weird mbn header, write it to that partition and then U-boot can load it.
Check: Adding OpenWrt support for QNAP QHora-301W - #205 by kirdes
For start you can just use the userpsace loader but you must manually reset the autoneg via register write on AQR for it to work after