For those of us who don't own the book it would be handy if you could supply a slightly more elaborated description of the problem.
However, <servlet-name> elements in <servlet-mapping> and <filter-mapping> should always contain a contents of a corresponding <servlet-name> in a <servlet>. So from what you say alone, I believe it is indeed a mistake.
Can you also have multiple <url-patterns> or <servlet-names> as of Servlet Spec 2.5. Is this true also for the SCWCD 083 exam?
You are certainly correct that Servlet 2.5 spec allows multiple <url-pattern>s and <servlet-name>s in a single <filter-mapping>, and that only one of these may have been used in v2.4 and earlier. An educated guess would tell me that only one element is ever going to appear in a <filter-mapping> in the exam, so you won't be asked peculiarities about how many elements are allowed - so it shouldn't be a problem as far as the exam is concerned. A more typical question would be to ask you to structure a <filter-mapping> tag via drag-and-drop, and there will only be one correct answer (hence can only be either a <url-pattern> or a <servlet-name> to be used).
Hope that helps.
Charles Lyons (SCJP 1.4, April 2003; SCJP 5, Dec 2006; SCWCD 1.4b, April 2004)
Author of OCEJWCD Study Companion for Oracle Exam 1Z0-899 (ISBN 0955160340 / Amazon Amazon UK )