Earlier quoted context omitted.
Android have been promising to finally tackle fragmentation in every release since KitKat. It seems people have a very short memory.
I think they did a great job at reducing fragmentation by pulling out most of the OS into upgradable components. All applications are upgradable, even Play Services are upgradable, and developers get the support library to get all the new things to all devices. So I believe they did a great job at reducing fragmentation in the sense that it no longer really matters what version you have, you still get all the newest…
That's not true (the most of the OS part). They untangled their own stuff (Play Store, Google services and so on) and can update those as they see fit. The OS stuff is still monolithic. Most of serious security issues still require full OS updates. Also supporting a new major version of Android runtime still require a full OS update.