And this is a perfect example of why it's virtually never in any multinational company's best interest to be a part of not just dubious, but nefarious government-sponsored misbehavior.
I've never seen an instance where this can be hidden for any significant period of time. Mind you, quite a bit of damage can be done before detection, but ultimately it's the willing dupe of a company that pays the price.
The problem with Chinese companies is that they have to run under China's government rules, which don't really leave "no" as a response they can make. But even the Chinese government has to know that if everything you produce gets caught up in situations like this in the international market, you're not going to keep that international market for long.
I'd also hope that multinationals that have their manufacturing done in China are doing random testing of product samples to determine if something underhanded may be afoot.