There's probably very little commonality left nowadays though. However, if you go back to the earlier days (Panther, Tiger, Leopard) and look at the release notes of Mac OS at the time, and the release notes of the contemporary FreeBSD version of the time, you'll see very similar text: I remember word-for-word paragraphs about things like NFS fixes in both.
Nor in NeXT, but it shows a history of Unix/FreeBSD development at Apple prior to the hire of Hubbard during the Mac OS X era. That is to say, his status as co-founder of FreeBSD and Apple hiring him wasn't merely a coincidence.
And to clarify my example, Fuchsia is set to be a Linux-less functional rebuild of Android, but it'd be a bit myopic to point out that "there's no Linux in Fuchsia". It's like saying there's no Steve Jobs in any Apple products created after his death. Less perhaps, but not none.
Can you share some source of your statement?