Please permit me to correct you. TLS 1.3 has never been blocked in China. In reality, what was blocked in China in 2020 was not TLS 1.3, but only TLS connections using ESNI. See: Exposing and Circumventing China's Censorship of ESNI. Because ESNI required TLS 1.3, some news outlets published articles that unfortunately gave the impression that all TLS 1.3 was blocked in China, and the misconception persists to today.
There’s another important difference between ESNI in 2020 and ECH today. ESNI was never seriously deployed. Cloudflare had server support, but it was not enabled by default in any browsers. Nobody was actually using ESNI. That is why, when ESNI was blocked in China, it was only noticed by a specialist who was experimenting with some custom software. It was quite unlike the blocking of ECH in Russia in 2024, which was immediately noticed by thousands of ordinary users.
TLS 1.3 still works fine in China. As far as I know, there is no evidence of ECH being blocked in China. (Except for the DNS and DoH/DoT censorship that already happens there, which could have an effect on ECH.)