The unverified part is no longer true. A lot of companies now get reviewers to buy the product from Amazon and reimburse them for their costs via PayPal. So in general, when it comes to obscure Chinese brands, you can't trust the Verified Purchase label any more. I stopped doing incentivized reviews with the rule changes, but I know that's how they operate, as I've had many offers to go the PayPal route.
I rely too much on Amazon for my own purchases, and it wasn't worth getting banned from reviewing for that.
What you're talking about tends to happen over facebook or wechat. But there are "Amazon Launch Services" which are far more pervasive in my experience. You'll find countless services like Viral Launch, JumpSend, etc. that find some way to make it hassle free to get those first few crucial reviews.
The funniest thing I've ever seen happen is one person was scamming the sellers. They would place the order, get paid via PayPal, and then cancel the Amazon order. It was cathartically beautiful.
Possibly for new items in the mainstream.
However for the long-tail of niche items the plurality of my Amazon reviews were the first and often they remain the only, particularly for older or out-of-print books.
Books on the other hand are probably sold by sellers who bought them used/returned/wholesale and are flipping them. They could care less about your product review because they almost always have only one or two copies.
Amazon tends to remove reviews in waves. I suspect this is so that they can use known fraudulent reviewers to catch unknown fraudulent reviewers.
As a seller, it was a great day to see my number one and two competitor have their product reviews dropped to almost 0 overnight. I didn't lose a single review. I hope Amazon keeps up what they're doing because it will only make things better.
P.S. Other things to look at are:
1. Many reviews in a short time frame (Only 1-3% of people leave a product review, so if you see 20 reviews in 3 days, they would have needed to sell almost 700 units! Not impossible for a very well established product, but a new one? Almost impossible, report it.)
2. The very first reviews. These are almost always fake and unverified. No one ever looks for this but it is the most common indicator in my experience of faked reviews given how low the bar is.
After protecting yourself, protect others! The best thing you can possibly do is to report violations!