to be exact, what it means is that you combine gellius into another unit for x2 base exp. so unless you have copies of gellius, vincent, kojuurou, julian and jerome lying around (for example), you're not really benefiting from it.
edit: also, it should not make your decision harder. in fact, it should make it easier because you now know what her SAW and AW are going to be so you can judge which will be better.