This is by design, and everybody should be aware of that. I don't know about glibc, but as far as the kernel is concerned, Linus has never guaranteed ABI stability. API, on the other hand, is extremely stable, and there are good reasons for that.
In Windows, software is normally distributed in a binary form, so having ABI compatibility is a must.
Uh, the kernel ABI is extremely stable. You could take a binary that's statically compiled in the 90s and run it on the latest release of the kernel. "Don't break userspace" is Linus's whole schtick, and he's taking about in terms of ABI when he says that.
This is about the ABIs of userspace "system-level" libraries, glibc in particular.
In Windows, software is normally distributed in a binary form, so having ABI compatibility is a must.