Linux is a kernel, FreeBSD is an operating system.
What follows is not actually a Stalmanesque rant, but I think an important point that needs to be made.
GNU, Android, and ChromeOS are all operating systems that use the Linux kernel. Microsoft Office is available on Android, but I don't think it is very easy to run it on GNU (eg Debian / Fedora / etc) without running it on some sort of Android emulator or Virtual machine. You can I think run it in ChromeOS.
So in that sense, there is fragmentation in "Linux".
That isn't necessarily a bad thing though. People have tried laptops running Android, and they were mostly useless, because Android isn't designed for that form-factor, and trying to run a desktop operating system on a phone would be an equally bad idea.