You were arguing that they didn't care about UNIX, which is demonstrably false, and they went to great lengths to get their OS certified; it is the core of their operating systems. This has been pointed out several times now.
You're right from the point of view of a GUI application developper, the UNIX core is somewhat hidden under intermediate layers, but then it's also the case for applications on Linux. Using GTK or QT, you don't deal with low-level kernel APIS much beyond POSIX either. And you can also do that on macOS, so it's a bit pointless as a purity test.
It seems difficult to argue with a straight face that Apple's developers working on the kernel, low-level layers and system libraries don't care about UNIX: that is their whole job. And as a user, you can have UNIX and decent GUIs.
That is a tiny slice of the OS, and macOS wouldn't be macOS without Objective-C / Swift frameworks, whereas GNU/Linux is still GNU/Linux regardless of what one puts on top of the Linux kernel.
macOS being UNIX was never in discussion, as mentioned it helps sales.
You're right from the point of view of a GUI application developper, the UNIX core is somewhat hidden under intermediate layers, but then it's also the case for applications on Linux. Using GTK or QT, you don't deal with low-level kernel APIS much beyond POSIX either. And you can also do that on macOS, so it's a bit pointless as a purity test.
It seems difficult to argue with a straight face that Apple's developers working on the kernel, low-level layers and system libraries don't care about UNIX: that is their whole job. And as a user, you can have UNIX and decent GUIs.