They would be a little surprised to learn that humans have souls at all. Not because they think they’re monsters necessarily, but to sprites, their souls are like little pieces of the Spirit they pray to. Since humans don’t have one of the Spirits connected to them, it would be a bit surprising to find out that they have souls from an entirely different source.
Knowing how powerful a soul is would be less of a surprise. Souls are nothing to be trifled with, no matter the source. They might be worried about where those human souls go, if they don’t have a Spirit that will take them in. Heaven and Hell would not be easy concepts for them to grasp.
Bowman himself would be as belligerent as he is about anything a human tells him. Especially if he can’t actually see or feel any proof of it. If he actually saw a human soul, he’d be both mollified and also wondering why it’s just kinda floating around. Doesn’t it have places to be. Free it.