Probably you should take in mind that this article is about difficulty to implement computer player. Not event to implement, but to make it efficient. And this task is more resource hungry for Go than for chess.
Also heuristics for Go are less ... uniform (not sure of right the word). The concepts of liberties, claimed territories and such are more abstract than heuristics concepts in chess, or so I've heard.
But I completely agree with you that the fact that much more effort has been put into chess software R&D than is has been done for Go software is an important point and has to be considered in comparison.