These are Apple IP. It's most likely a violation of Apple copyrights and design patents to use them publicly or in a commercial context (aside from referencing them in CSS or displaying them using the proper macOS API calls).
(IANAL) … no, not "doubly so". See https://en.wikipedia.org/wiki/Fair_use, in particular, "Amount and substantiality" and "Effect upon work's value" ; I think such a use would be ruled fair use, if you, e.g., happened to have a Macbook incidentally in a photo of a coffeeshop. The MBP is not the sole focus of the shot, and any decent looking laptop could potentially stand in for it. You're not detracting from Apple's revenue selling laptops as a photo isn't a laptop. (Hell, if anything, in the right light, it's free advertisement if it advances Apple's product as a status symbol?)
Vs. here's the cursors, here basically a direct copy. (As opposed to incidentally in another copyrighted work.) If you were to just download them an use them on your personal laptop, I doubt Apple is going to care, but if you download them & used them in a product … they might. The beachball is iconic (for better or worse).
Some of them are rather generic, and look only imperceptibly different from those of other vendors (e.g. resize arrows) – IANAL, but for those, I think copyrightability (threshold of originality, purely functional vs creative elements, etc) is open to question. Whereas others (e.g. busy) are much more distinctive, and I think the odds of them being protected by copyright (and trademarks too) is much higher.
"the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright."
