No, Thanks (in Advance)!
Taken literally, they are saying, "I'm thanking you right now for something that you haven't done yet. I don't know how well you will do it, so you may end up not helping me at all, but thanks anyway." That kind of 'thanks' doesn't strike me as very meaningful. Instead, it seems a lazy way of checking a social norm box.
When someone does something exceptional for you, thank them at the point of delivery. If they tried their best but didn't end up being that helpful, you can still thank them (for their efforts, at least). Yeah, it might be one more e-mail clogging up somebody's inbox, but that is a small price for preserving a sense of value in the work that we do well.