You can attach your wooden grip to the Chinese stock, if you also replace four imported parts with US-made ones. Unfortunately, the stock / handguard are the two most popular parts to replace because of their availability. If your set on using the Chinese stock with your grip, you will have to swap out a different part. You could also attach your pistol grip to a US-made conventional stock, at which point you would only need three more parts.
What's so nasty about the pistol grip: Pistol grips are on a vague and semi-constantly morphing list of "restricted features" the government has decided would restrict an SKS from importation. They have further decided that if an SKS can't be imported with a pistol grip, you can't add one once it's here either. It's a seldom (maybe even never) enforced regulation, so a large number of people are either unaware or just don't care.
Despite what is said publicly, this whole thing is a crazy way to keep low cost imported firearms out of the USA. This keeps prices up, protects US manufacturers and restricting poorer citizens from purchasing a firearm. So you're correct, these rules can sound strange times . . .
Larry
PS: there are some stickies at the top of the legal forum which describe this in more detail. You can also check out the link in my sig if you feel like you want your head to explode.