I think this is a matter of perspective. I think Mac OS is just about as innovative on Unix as Linux is. Not in exactly the same ways mind you but definitely they’ve invested more than just wrapping a shell around POSIX.

Keep in mind the original post was going so far as to talk about a having different protocol stacks (not TCP/IP), different display protocols, and different IO ports (Apple devices do have some of the latter). And if JPEGs aren't supported through libjpeg, we're actually talking about a completely different computing paradigm, so it's not even a von Neumann architecture. In the fact of that staggering amount of difference, the slight difference iOS and current MacOS have from Linux and Windows is very shallow. That for many things you can easily throw a compiler on there and compile the same open source project and it will link to the already existing libraries it needs, the same ones it will find on other platforms, shows this.

While I don't know enough to comment authoritatively on it, I think with respect to this Apple might have taken a step backwards (at least with respect to percentage of system that is unique, if not in total amount of libraries and code) when it switched to OS X. OS 9 and its prior versions were an entirely unique and custom OS designed at Apple. The whole switch to OS X was taking a UNIX core for stability and building on top of it.

Apple systems are quite different than the norm in many respects, but the scope of this discussion is so large that there's really little they do that's different than everyone else from that perspective, because nobody does anything different. It's hard to start from scratch and ignore approximately 80 years of concerted computer science effort and come up with something useful and usable in any sort of time frame that makes it worthwhile.