Before the rewrite all the GNU utilities were in the base OS. How large a percentage that was to the rest of the base I couldn't say off the top of my head. But all the GNU utilities were in there as well as the compiler suite which has also been removed and replaced with Clang/LLVM.
according to FreeBSD's own site, their GPLinBase tracker, you're incorrect. Only a handful of GNU or GPL stuff was ever in base, and your example of 'tar' isn't one of them.
Then it's missing in that site. BSDtar was the replacement.
I remember having to use different flags for bzip2 (j vs y) in tar on FreeBSD vs Linux about 15 years ago so I was sure they were different, but I have an image of a FreeBSD 4.10 box from June 2004 and /usr/bin/tar is indeed GNU tar.
It's not missing from the site. FreeBSD never used GNU tar. FreeBSD used a very small number of GNU utilities. tar, coreutils like ls, cat, etc. where never used. It was mostly things around the GNU toolchain, which ARE mentioned in the GPLinBASE wiki on the freebsd site.
FreeBSD's tar(1) man page says it used GNU tar from FreeBSD 1.0 until 5.4 when they replaced it with their own version.