Saying "Strogatz did once beat a grandmaster in chess" without specifiying that it was simultaneous exhibition is a lie by omission. I am a chess player, and I would never insult another player by claiming to have beaten him or her without specifying the format. There is a way for you to say what you want to say without exaggerating to make a point.

What's the threshold for someone serious enough to write a chess article?

There's no threshold whatsoever, as long as you communicate a respect for the game and you don't try to use chess as a metaphor to make a larger point about AI and humanity that doesn't hold up to scrutiny. If a rank amateur can appreciate that AlphaZero plays chess beautifully and wants to write about it, by all means. I happen to agree. Just please don't abuse my beloved game for marketing purposes or to win an argument.