There’s a fundamental difference between Communist Party membership in western and in Communist countries.

A Communist Party member in America is enlisting in a totalitarian organization meant to destroy the country and replace it with a Communist dictatorship. In China, a Communist Party member wants to improve their career prospects and get close to the elite. It doesn’t tell you that much about him or her. In America, a Communist is a committed ideologue, in China, it’s entirely possible that he or she is just joining the mafia that runs the place.

That’s also why Cold War screenings of Russian immigrants for membership in the Communist Party or its affiliated organizations was mostly meaningless. Actual spies stayed off the radar. 

That doesn’t mean that the huge leak of membership names isn’t significant. But, unlike screening for PLA membership, is less likely to reveal operatives.

China is Communist, on paper, but mostly, like Putin’s Russia, nationalist. The spies it recruits are nationalists first. And Chinese citizens going to the United States or other foreign countries are routinely asked if they will cooperate with government intelligence gathering operations. That means a wide base of operatives in the tens of thousands and perhaps even the hundreds of thousands. Communist Party membership does suggest a greater willingness to collaborate, but lack of it doesn’t mean anything either.

Finally, the names of Communist Party members working for US companies that handle defense contracts are mostly meaningless because they seem to involve personnel working in China. Any US company with a Chinese office is already compromised, at least as far as that office goes, whether or not its employees are officially Communist Party members or not. A US office in enemy territory, which is what China is, has already been surveiled, its communications are monitored, anything being sent to or from the phones of its employees and executives is intercepted, and some of its local employees are passing along information.