I actually think this is a great application for AI. "Hey AI, look at these 2 million trees and tell me which ones look similar to this one."
It identifies a bunch of trees and even though it identifies a bunch that aren't similar then you have a much smaller list to sort through. It doesn't have to be right all the time, it's just helping narrow it down.
This is way different from "Hey AI, what time does the show start tonight", where if you get it wrong 10% of the time then it's a useless tool.
Unfortunately it doesn't quite work that way. The dataset they are training it on contains images of a single tree, so it's ability to generalise to a normal tree of that species will be incredibly limited.
Consider a facial recognition algorithm trained only on images of Nicolas Cage, then being tasked with identifying members of his family. It would do very well at identifying Nicolas Cage in a crowd, but probably not a good job of identifying anyone else.