I'm only speculating, but I believe that Darwin is much more bare or stripped down compared to universal Windows. I believe that the author was refering to bein

I'm only speculating, but I believe that Darwin is much more bare or stripped down compared to universal Windows. I believe that the author was refering to being able to run iOS apps on OSX and vice versa. This IMO is not very smart. Each platform, mobile or desktop, has a different purpose and requires different things. So to make a universal OSX or iOS it means that either you make a significant amount of compromises which don't benefit either platform and each suffers. Or you build everything into the core and it ends up being a complete and buggy mess with a bloated install size.