I used rf to make the backup, and it ended up giving me 6 backup files *.lunX (0 through 5). I was then able to use wf *.lunX --lun=X to restore successfully.
Code:
python3 edl --loader=Loaders/qualcomm/factory/sdm855/000a50e10029003c_ec70ff124179a138_fhprg.bin wf deviceBackup1.lun5 --lun=5
I realized there's one last thing I need to do before making further modifications. Does anyone know if there's are hardware key combination Boox uses to boot into EDL mode? Else would an EDL cable work?