Basically Kingston (I think?) and a few others released a new SSD and used very high quality components in them, so that they exceeded advertised specification. After the early-adopter reviews came in with the benchmarks and whatnot, they altered the build to use lower quality / cheaper components. When discovered and confronted, their argument was that the lower quality builds still met spec, so it was appropriate to sell it under the old model number and listings, but the upshot was that they got to produce low quality products while benefiting from reviews and benchmarks that were run against a higher quality product.
I don't think there's much Amazon can do about this particular issue... although yes it would be a great help if you didn't see reviews for the 900x version of something while looking at the 1x version page.