As pointed out by @Norilinde, this is not in fact the case. However, that doesn’t mean that blood drives will do the trick.
The bit of Game 2 Ch 1 I’m working on right now will make the dilemma clearer. For anyone who wants to wait until then to find out, I’ll put the reveal in spoiler tags: pain isn’t necessary, but for aetherial blood to be potent enough to be useful, something that rhymes with “pain” is. And anyone who took the full “sabotage Harrower” path in Game 1 should be able to guess what that is.
I wrote a bit about the history of the Xaos-lands here, for reference. The Brauracha who live(d?) there are cousins to the Nyr and Halassurqs, and were pioneers of Theurgy/Goety. The Xaos-storms preceded the Wards, but not by long.