Communist China would definitely have an interest in giving arms to a force fighting both the US military and Russian-allied proxies in a neighboring country. [China has also helped Iraq and they helped Yugoslavia - why else do you think the US really bombed the Chinese Embassy?] They also know the US would not invade China if the weapons were found, because they know the US govt knows they (China) have nukes and are not afraid to use them.
None of this precludes other side deals with the bin Laden/Taliban crowd to get them to call off the Uyghurs. This isn't very different than the US going substantial aid to the mujahadeen war against the Soviets while US bases in were left largely unmolested as jihadists directed their energies elsewhere.