Right. This is not just Mac OS, same thing can happen on Windows. Modern media DRMing sometimes involves bypassing your OS entirely[0]. Audio/video streams have special hardware paths through the CPU and GPU. HDCP uses encryption to create a safe pipe between the incoming stream and your monitor, so the data can't be snooped on or modified mid-flight. Etc.

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[0] - Or at least almost entirely, I suspect at least the kernel must get involved somehow. Otherwise Widevine support wouldn't be an issue on Linux the way it is (or was).