A UNIX™ certification is not the same as being actual code from Unix™.
NeXTSTEP was 4.3BSD plus Mach, using Display Postscript as its windowing system and TIFF as its image format, supporting transparency for icons. macOS is FreeBSD plus Mach, using Display PDF as its windowing format and PNG as its image format, supporting transparency for icons. Basically NeXTSTEP but every component upgraded to its then-modern equivalent. (Except Objective C, they kept that.)
The issue at hand was me making an analogy about how Meta releasing LLaMA to many .edu addresses still would not mean that LLaMA would be actually used widely, since the Unix™ source code was similarly released by Bell Labs, but the actual Unix™ source code did not end up being the code which we now use.
The fact that UNIX™ later went on to become a compatibility specification, not a specific implementation, is irrelevant to the analogy.
NeXTSTEP was 4.3BSD plus Mach, using Display Postscript as its windowing system and TIFF as its image format, supporting transparency for icons. macOS is FreeBSD plus Mach, using Display PDF as its windowing format and PNG as its image format, supporting transparency for icons. Basically NeXTSTEP but every component upgraded to its then-modern equivalent. (Except Objective C, they kept that.)