I don't think I have ever seen chalky looking pearls in person, just in some bad internet photos from some shady companies.
Now, I have seen some freshwaters here in Japan that seemed like seed pearls. They were fashioned into a multi-strand torsade, and it was an exquisite aged-ivory color. The jeweler told me they wouldn't hold that color long because they were freshwater. Of course I wondered if they were dyed, but he didn't know. But he was showing me the strand as an example of Chinese freshwaters because it was they only ones he had. Not a huge shock in small town Japan. Lots of Akoyas, lots of Tahitians, but that was mainly it.
The reason I bring this up is the color question. In very tiny pearls, would white pearls tend to show a yellowing with age? Or is this more due to treaments wearing off? Or could it have just been a translation problem? I guess he could have been referring to the luster, but I know he said the color would change. Any thoughts are great.