The tag is present in Lintian version 2.104.328. That is the most recent version we know about.
The classpath listed in some of the files references files outside of /usr/share, while all installed JAR files must be within /usr/share/java for libraries or /usr/share/package for JARs for private use.
The rationale is that jar files are in almost all cases architecture independent and therefore should be in /usr/share. If the jar file is truly architecture dependent or it cannot be moved since symlinked jar files are not accepted by the application, then please override this tag.