Granted their party's position is more nuanced than my initial comment made it out to be. They still say China, post Mao, became revisionist.

Prolewiki

PSL stands in critical support of China but they hold that it has undergone a Revisionist turn, alleging that Deng Xiaoping took the PRC down a 'Capitalist Road'.[7] Repeating the unsourced myth that Mao denounced Deng as a Capitalist Roader. Despite this, they support China's socialist development and are sympathetic to Socialism with Chinese Characteristics.[8]

PSL further stated that there was a new Capitalist Class grown within the PRC which collaborates even as it struggles with Imperialism. In 2023, Brian Becker reconfirmed PSL's 2007 stance of China.[9]

Here they call the CPC leadership, including Deng, 'capitalist roaders' 10 times.

There's some other documents of theirs linked in the References page that don't read great but at the same time they'll whip out something like this,

People outside of China, especially those who hope to build a socialist future for their own people, who yearn for a world of justice, equality, and peace, should join in supporting the efforts being made to find a path to “socialism with Chinese characteristics.” We should be critical when necessary, recognizing and acknowledging the problems and the mistakes which may be made as China advances, “crossing the river by feeling the rocks.” But we should support China’s project of socialist development, support the leadership of the Party and its work to control and redress the abuses and errors which arise, support the hopes and the hard work of the Chinese people. Most importantly we need to defend China against the aggression of American-led imperialism, the rising tide of a new Cold War, the unremitting demonization of China.”

So perhaps I was in error to say, "their official position is that China isn’t socialist" as their position is obviously more nuanced or internally divided.