That may be true but a large core of it is still BSD. In fact, it’s so BSD that one could create a BSD distro based off FreeBSD and achieve binary compatibility on x86. Which is exactly what RavynOS [0] has done. There’s a lot of BSD under the hood of macOS still today in Darwin. A mix of FreeBSD, NetBSD, and OpenBSD.

[0] https://github.com/ravynsoft/ravynos