"It could only be invented by humans" is a very different statement to "no aliens will have invented it". That's making an ought out of an is.
The intention of the GP was - given that Go was not invented again on Earth, there's no real indication that it would be invented again at all. That doesn't imply that it cannot be invented again because it is too complex.
I'm not following how this logically follows at all. It was invented here, so if anything, its invention here is a great data point that it could easily be invented elsewhere too (take a Bayesian approach to it). I don't see how its invention here somehow counts as evidence against it being invented elsewhere! There are an infinite number of games that haven't been invented here; all of those would seem to be much less likely to exist elsewhere than ones that actually were invented here.
Also, it's kind of silly to count something not have being reinvented against it, because things almost by definition cannot be reinvented. Look at how popular board games are right now; if Go hadn't yet been invented, it's quite possible that it would be invented now. But instead it has already been invented, so people already know about it, and any would-be inventors end up not being inventors; they either already know about it or are told that what they've come up with already exists.
> Also, it's kind of silly to count something not have being reinvented against it, because things almost by definition cannot be reinvented.
Well, they can, but the opportunities are limited to cultures where the game has not been introduced yet.
I would also point out that we don't know that Go was never invented independently on earth, just that it was never invented and popularized in a manner that left a cultural or historic record of which we are aware. If Go were played by a small clan of prehistoric people using different color berries and a grid scratched out in the dirt, what evidence would be left?
So that REALLY limits the opportunities to cultures that left a significant historic record but had no cultural exchange with china.
That's an argument that only works on logicians, along the lines of "every dice with enough sides is actually rigged to the first number it lands on". If a particular consequence is exceptional (the invention of Go), but some consequence is inevitable (the invention of a board game to pass the time of some people in China), analysis after the fact has limited meaning.
> "It could only be invented by humans" is a very different statement to "no aliens will have invented it". That's making an ought out of an is.
Not quite. It's making a must out of an is. The relevant distinction is "true by necessity" vs "true by coincidence", not "factually correct" vs "morally correct".
The intention of the GP was - given that Go was not invented again on Earth, there's no real indication that it would be invented again at all. That doesn't imply that it cannot be invented again because it is too complex.