I mean, the source even says that "Due to the sheer number of possibilities in Go, traditional “brute-force” search trees which run through all legal variations are not only highly inefficient, but also implausible to implement in a time-constrained scenario."
Seems to me like it is saying that even without as strict of time-constraints that its effectiveness would be difficult if it relied solely on a brute-force method. [EDIT: I also would say that the time-constraints are a part of the game and as such the fact that brute-force methods are inefficient due to said time constraint does indicate the issue as well.] It also doesn't need to rely so heavy on its own capacity for abstract thinking when it relies on looking at numerous games people have played. Compare this with many types of chess AI where they can create professional level AI without having it need to refer to records of human-played games.
I'm not saying that the AI hasn't been able to overcome large hurdles, but I think that it is undeniable that the approach to building the AI shows how different the thinking required is for Go in comparison to games like chess.