He says, as he quotes a paragraph that specifically calls out SmartOS and OmniOS -- both of which are under the IllumOS branch of OpenSolaris.
"So, CoreOS is the Linux option he recommends? The same CoreOS that uses SystemD?"
The problem he's raising isn't that linux is going to be different, and if you think it is you need to re-read. Try doing it with your --with-reading-comprehension switch. It being different is just a statement of fact, the problem statement was separate.
CoreOS is not a distribution in the classic sense. It is a platform for deploying containers, and in the use-case they've setup the author clearly believes it will allow you to still be successful in spite of systemd.