Err, no. While the primary source rule is used to sort out contradiction rules between books, it's not Core > Everything else. It's Setting Book > Book Focus > Everything else. For example Lords of Madness, which focuses on abberations and mind flayers is the primary source for abberations and mind flayers and any book that conflicts with anything written with LoM is wrong unless it's setting specific (This continues with the other Monster books like the Dragonomicon and Races of Dragons, and the Magic Item Compendium). The Rules Compendium, which focuses on rules trumps all other sources of rules that it covers (just as the MiC does with the custom magic item generation).