for example tar(5) website version date: December 23, 2011 system running 10.1-RELEASE: November 1, 2012 https://www.freebsd.org/cgi/man.cgi?query=tar&apropos=0&sektion=0&manpath=FreeBSD+10.1-RELEASE&arch=default&format=html
The date in the manual page on the site is correct. gjb@nucleus:/freebsd/src/base/releng/10.1 % grep ^.Dd contrib/libarchive/libarchive/tar.5 .Dd December 23, 2011 It seems you are comparing tar(1) versus tar(5) on the running system, based on the dates provided.
You're absolutely right