Interesting. You mean the "computer guy" claimed Mac OS is a derivative of Elementary Linux? Actually quite hilarious if he really said that. Its of course the other way round: Elementary's UI is heavily inspired by the Mac; so probably he mixed that up somehow.
Elementary is in no way a precursor of Mac OS. Not only is Elementary waaay to young, all its got in common is that both Mac OS and Linux are kinda Unix-ish, where Mac OS is actually derived from Unix, whereas Linux an attempt of a Unix reimplementation; or, as Linus Torvalds puts it: Unix-like.
Mac OS is based on the Mach kernel and in itself is derived from NeXTStep, which used some parts of FreeBSD's and NetBSD's Unix implementations.
Mac OS (Leopard, I am not aware if this is true for newer variants as well) is UNIX-compliant and was in parts certified.
Not that important really, this is just fyi. There is a fair bit of misinformation out there on Linux and Mac OS and how those are historically related, so I sometimes feel obligated to straighten that up.
Thank you. Always good to have the correct information. I knew that MacOS was based on FreeBSD a Unix variant but that was about the extent of it. I only try out these various systems, I am in no way an expert on Linux or Unix. But it is fun to set them up and use them from time to time. As for the computer person, his channel is called Explaining Computers and he has some pretty good info. One of my favorites was a video on Ubuntu Studio. He is pretty sharp so I may have just misunderstood him. He is really into it though so it might be interesting for you to check out, I use him as a source for finding new system to try out.