Soma can collect souls from all of the enemies he faces, including Dracula who is technically the same person as Soma. However, the only being that you cannot get a soul from is Menace. Why? It's an amalgamation of many demons and souls! It cannot give Soma a soul because it doesn't have just one soul to give!
Alternatively, it's possible Menace is the "one" soul Soma actively refuses to take with the Power of Dominance upon defeat. After all, the last time he defeated Menace, all of the souls within it flooded into his body, threatening to overwhelm Soma if not for some last-second Heroic Willpower that allowed him to survive and reject the influx of souls. Probably not an experience he'd want to relive.
Charlotte's Binding Book may come off as weird, as it requires her to copy spells off of her foes, which is something she and Jonathan don't share with the other DSVania protagonists... until you remember that in PoR, a good portion of her spells were dropped by enemies and were essentially the same attacks they used. Charlotte absorbing the spell from them is just her cutting out the middle man!
