No experience with these. My experience is that backpacking gear is still a pretty honest game, and you get what you pay for. Generally, the rule is: Light, cheap, quality - pick two. My guess is that the Chinese duck down bags fit the light/cheap category, and quality (accurate rating, down quality, etc.) is not a consideration. You need to read reviews carefully, too. I’ve seen huge numbers of reviews that give a product 5 stars and begin “I haven’t actually used this bag/stove/pack yet, but I’m excited to try it out...” or “Ive never backpacked before, and will use this on my first trip. It looks awesome.” There’s really no need to read further in such reviews; there’s no way the rating can be accurate when the buyer has not actually used it, and has no experience against which to rate the build quality.
Go with a known, quality manufacturer; you’ll never regret it.