The mod_autoindex.c module is part of the Apache HTTPD server, not the Apache Tomcat server. The clues are in its name. First, and foremost ".c" means C programming language, not Java, and Tomcat, unlike Apache HTTP (more commonly known as simple "Apache"), is all Java.
If that wasn't clue enough. Anything named "mod_something" is almost certainly an Apache module.
Tomcat will index any directory within a webapp providing that there's nothing defined in web.xml that maps to the equivalent relative pathname. And, of course, providing that Tomcat has read-access rights to that directory. Although for directories within a WAR, that should always be the case.
Some people, when well-known sources tell them that fire will burn them, don't put their hands in the fire.
Some people, being skeptical, will put their hands in the fire, get burned, and learn not to put their hands in the fire.
And some people, believing that they know better than well-known sources, will claim it's a lie, put their hands in the fire, and continue to scream it's a lie even as their hands burn down to charred stumps.