The email exchange at http://www.mail-archive.com/users@maven.apache.org/msg90985.html
says:
“This is all theory… Perhaps while writing the docs, someone involved with Maven development thought it might be useful to have a src/main/config directory and so it was included in docs, but since it was never implemented in the code, it is not being used today.“
and
“The directory [src/main/config] doesn’t show up on the classpath so the application or test classes
can’t read anything in it.“
So just use src/main/resources.
Note: I don’t know if this is true (I’m the question asker), but that would explain why so many people on the web recommend src/main/resources for log4j.properties. If people agree this is the right answer could you let me know (comment or vote) I put it here to save other people the typing.