I've seen this phrase repeated over and over again and I don't think it is true, or at least, to the degree that "benchmaxxing" claims are true, American frontier AI companies are probably about as guilty of it as Chinese AI companies are.
For both GLM 5.2 and Kimi K3 I feel the rough average of the benchmarks gives you a rough idea where they stand. GLM 5.2 was sitting somewhere behind Opus 4.8 but it didn't feel very far away. I've used Kimi K3 via OpenRouter and while I've had limited experience so far, it sure as shit feels like it's right up there with Sol and Fable to me. I am happily able to believe Fable has the edge still, but on a request by request basis it would be pretty easy to get an impression one way or another.
The existing Kimi models were already pretty good so I really just don't find this new model to be that hard to believe. Maybe I'm naive.