Its not a guise of security, it actually accomplishes it. Mac malware now has to operate within the confines of these permissions and nowadays the author has to submit a sample of the malware to Apple before it can be opened without insane prompts (this also means losing $99 and attaching their legal identity to the malware/committing identity fraud). If Apple went full-iOS on MacOS and made it so "everything must go through the App Store" then the possibility of mac malware would effectively disappear overnight into the same realm that iOS malware currently resides: jailbroken iOS devices with shady (mostly piracy-focused) apt repos.
Realistically, malware only affects a tiny fraction of users, and only a further tiny fraction suffer demonstrable loss from it.
For a certain generation of adults, going to visit your non-technical parents socially meant budgeting extra time to eradicate the adware of the month. It was a constant problem affecting large swaths of users, and fixing it was beyond the technical ability of most people.
Edited: fix typo.
Their whole design is incredibly neat and well done! If you like these features (or just don't care) the default install does make attacker's lives harder.
But if you disagree with these features or just don't like them you can just boot into recovery mode, authenticate with your password and disable almost everything for macOS.
And if you just like the hardware you can do the same and install a custom kernel like Linux or *BSD and do whatever you want.
You can even have triple boot into one macOS with full security enabled, another macOS install with everything disable and a third "macOS" which actually is Linux.
They spend a lot of effort and engineering time to make all this possible.
you can also just map the same physical memory once as rw- and once as r-x even with SPRR enabled there.
If I understand correctly, one of the big unsaid implications of this article seems to be that it is now impossible to have RWX, because the hardware completely prevents it. APRR looks more like a general permissions-remapping mechanism, while SPRR appears to go beyond that.
While the technical details are certainly interesting, IMHO it's also disturbing in the same way as weapons of mass destruction or DRM. This technology is used by one company to essentially maintain control over its users, under the convincing guise of security.
What do SPRR and GXF stand for?
Given the functionality, my guess is APRR = Access Permission Remapping Registers, SPRR = Secure Permission Remapping Registers, and GXF = Guarded Execution Feature.