This line in Docs.gmk is incorrect, and should be removed.

    -tag version \

It incorrectly enables support for the @version tag, which should only be enabled by the (poorly-named) -version option. (@version and -version are a similar pair to @author and -author).

A small number of java SE API files contain a very-old @version tag, and this started showing up in JavaSE docs in JDK 8. You can find these files by grepping recursively for @version. The change that added this line is probably a side-effect of adding support for the @apiNote, @implNote, @implSpec tags.

Note that removing this line will change the Java SE API docs, reverting the handling of @version back to its original treatment of being ignored up through and including JDK 7.