It's not so a surprise, as what is going on has been happening for a while now with Chinese bond yields being historically low for some time now.

As the Financial Times writes:

Every slice of China’s bond market has now succumbed to Japanisation - (Archived)

Back in November 2024, China’s 30-year bond yield fell below Japan’s for the first time in history ... A year later, China’s 10-year yield also fell victim to Japanisation ... That was “a historic crossover that may reignite fears the world’s No. 2 economy is sliding into the deflationary spiral that paralysed its neighbour in the 1990s” according to Bloomberg at the time ... Then, in March, two-year yields did the same. And last week, even China’s 12-month bill yield briefly moved below Japan’s ... There’s no secret to what is going on here. Japan’s economy has finally emerged from deflation.

... Meanwhile, China’s economy is sluggish, Chinese real estate continues to struggle, the debt overhang is monstrous, and the country’s demographics are bad. Plus, some investors think Chinese bonds are an attractive, safe diversifier for portfolios, weighing further on yields.