Much of the macos Unix userland is from FreeBSD as are some parts of the kernel, such as the ip stack. Check the man pages for cp and friends in mac and I believe they still reference FreeBSD.

> And the received wisdom about long options in the BSDs is a quarter of a century out of date.

Incidentally, so is much of the FreeBSD code. Many things were taken once, never updated from upstream again. I think a lot of the userland did get an update somewhere around 2014... all of a sudden, cal would highlight the current date, years after that happened upstream. But the IP stack hasn't gotten any updates from upstream AFAIK, probably because Apple customized it and it's too much work to merge in improvements that probably won't be noticed on client systems (things like syncookies).