So a "cathedral" must be "coherent" to be a true Scotsman?
Coherency cannot be measured, and it's extremely subjective. The *nix world can be extremely coherent: for example, you'll always find libtool, whether you want it or not, and your '70s-like filesystem layout. Isn't that "coherent" with its history?
This is not true even of Android and iOS, the modern wonderchildren he cheers on: a quick look at the Android filesystem hierarchy will show its adherence to outdated conventions (etc?) and incoherent repetition (sys? system?), and I bet you'd find something similar in iOS. So there might be a "coherent vision" behind, but the practice is quite incoherent; and mind, we're talking about very basic OSs that delegate any but the most basic functionality to third party apps. I'm happy to bet that in 10 years, the Android codebase will be as shitty and crufty as any Unix.
The truth is that a cathedral, in phkamp's rant, is "software that can all fit in one's head". For all operating systems, we're well past the stage where a single genius architect could envision the totality of a massive cathedral, for a number of reasons (time, working culture, legacy tech etc). Clearly phkamp, being more intelligent than most, only just passed that threshold with the very latest FreeBSD release, and felt the urge to tell the world.