MacOS isn't Darwin and comes under terms that do not fit rhe criteria of the exception. Apple actually did go to some lengths in the past to ensure that all layers of MacOS contained bits that they could claim restrictive licenses on.
A project like PureDarwin, however, can be freely distributed because it omits Apple's proprietary parts.
Basically all linux distros fully run without the closed source parts, they are only there to provide support for specific hardware. MacOS on the other hand cannot run at all without the closed source parts.
The line is that an open Linux distribution will boot and run on hardware that is sufficiently compatible.
The full MacOS as distributed by Apple is engineered to require closed source, non-redistributabe components even on the hardware it is most compatible with. It will completely stop functioning if you remove those parts. The presence of freely licensed components becomes de facto irrelevant.
A project like PureDarwin, however, can be freely distributed because it omits Apple's proprietary parts.
This law describes as a true-false something that is not only true or false. This law is poorly written. Amending it didn’t fix that.
The full MacOS as distributed by Apple is engineered to require closed source, non-redistributabe components even on the hardware it is most compatible with. It will completely stop functioning if you remove those parts. The presence of freely licensed components becomes de facto irrelevant.