Not necessarily; an encyclopedia isn't just an unconnected catalogue of facts--at least, it's not supposed to be. An encyclopedia article about a given subject is supposed to show the subject as a connected whole; it will contain facts, but will also contain important relationships between the facts, general principles, theories that explain the facts, etc. If you have that kind of knowledge of a subject, you don't have to memorize all its facts, because you can easily get to them from the facts you do have memorized via one of many interconnections.