From a lineage point of view, that is correct; but the original post was discussing the genetics issue, and from that perspective it is a misleading statement. Yes, everyone would be descended from Noah and his wife, but the genetic pool is much larger than just that, because the wives of Noah's sons are not the offspring of Noah nor his wife. While it is inevitable (assuming for the moment we take the Noah story as factual) that we are all genetically related to Noah, there is no actual requirement that we be genetically related to his wife, since theoretically that genetic information could have come from any of three other sources. Specifically, the mitochondrial DNA that we carry today did not come from Noah's wife, it came from one of the three wives of the sons of Noah, and the same can be said for at least half of the rest of the human genome.
Any offspring of the wives would be the grandchildren of Noah and his wife, and thus still "descendants of Noah and his wife", and so would any of their children's children unto the Nth generation
Of course; but I think you may have missed the point of the original post. Supercat's objection (an objection to which I tend to agree) was that a single breeding pair would lack the genetic diversity we see in humanity at this point. But in the case of the story of Noah, we actually have much more genetic diversity than would immediately be apparent.
If the story of Noah were literal, there would be less genetic variation in every other critter on the planet (except for the clean critters) than is found in humanity. However, any two humans from anywhere on the planet are more genetically similar than are two chimpanzees from the same troop.
Geneticists point to a genetic bottleneck in the human species about 70,000 years ago which reduced the population to less than 2,000 breeding individuals. Biblical literalists would have you believe the human race was reduced to eight individuals less than 6,000 years ago. The genes don't bear that out.
In addition, every species but the "clean" species were supposedly reduced to two breeding individuals less than 6,000 years ago (the clean animals got lucky with 14 breeding individuals each). If this were the case just about every other animal on Earth would evince less genetic diversity than humanity. The evidence does not bear this out. Indeed, I can think of only two animals in worse shape genetically than humanity -- dingos and cheatahs.