The name was changed from Brown Abishai to Krathbairn, meaning "Krath's babies". They basically took Krath's, a brown dragon, children and altered them to what, mechanically speaking, are pretty much "brown abishai" since the abilities are totally similiar.
However, the blackspawn corruptor and the hoarder are not in this book. They were cut most likely for space reasons.
Also, the other section cut was the guidelines on worshipping and serving the draconic deities of the draconic pantheon. But Eytan's write-up for the Web Enhancement will feature each draconic deity from 2E's "Cult of the Dragon", hopefully with a summary about each, their deity status, alignment, portfolio, favored weapon, and their role in the present day Realms. I'd love to see how he tackles the task of writing up on the 3 unique draconic deities of Faerun, personally (well 4, but one got destroyed and assimilated with another during the Time of Troubles). Zorquan was one I was interested in, particularly.
We've also been trying to convince Eytan on the WotC boards to allow Sardior a role in the Realms, as well.