That is to say that a player ranking within the top 1000 of a game like Go is a master of the game. A human player will take 10 years and way north of 10000 hours to get to where AlphaGo is.

There's no clear definition of "mastery." Honinbō Shusaku was a master. Honinbō Shūsai, Go Seigen, and Minoru Kitani would also be considered masters. As time marches on, average player skill increases. While Honinbō Shusaku was among the strongest players of his day, he would be hard pressed to hold his own against professionals in today's era.

I think it's fair to say that anyone who reaches shodan (1 dan professional) plays at the master level. The difference between 1 dan professional (1P) and 9 dan professional (9P) is three stones, or roughly 30 points. In amateur play, for comparison, the difference between a 1 dan and 3 dan is about 2 stones (roughly 20 points).

AlphaGo won 5 straight games against a 2 dan professional player. That puts AlphaGo around 3P, well into the master range.

In Go, the ranks are:

    30 kyu amateur (never played)
    1 kyu amateur (understands the game)
    1 dan amateur (mastered the basics)
    7 dan amateur (nearly professional strength)
    shodan (1 dan professional)
    9 dan (top ranking professional)

https://en.wikipedia.org/wiki/Go_professional#Discrepancies_...

"Traditionally it has been uncommon for a low professional dan to beat some of the highest pro dans. But since the late-90s it has slowly become more common."

We'll see in March how it does against a 9p.

Your comment was a perfect example of the superhuman fallacy - where a 3p+ AI becomes 'low ranked'.

Who, and where, I've not come across such a claim.

There is, of course, a question of whether a particular AI tool demonstrates value for money in a particular commercial niche. But not being so doesn't mean it isn't 'real' AI or 'real' intelligence. There are plenty of situations you wouldn't be value for money for me to invest in, I don't take this as meaning you aren't intelligent. It's a quite different question.