Binary package hint: apparmor
The latest changes in natty to allow multiarch paths for apparmor use /lib/*-linux-gnu/ in their paths. This is sufficient for all the architectures Ubuntu supports, and it's sufficient for native binaries on these architectures, but multiarch is intended to be fully cross-platform and be usable for binaries for other kernels. Even if apparmor itself doesn't run on BSD, Hurd kernels, Debian builds packages for these architectures and these will be cross-installable on multiarch systems... and some of them may even run, by way of kernel syscall emulation layers (in-kernel, qemu, etc). So the apparmor abstractions should account for this and not be limited to linux-gnu triplets.
(This is obviously a low-priority edge case.)
FWIW Stretch was released for Linux architectures only, and I doubt it'll change any time soon. I believe the Debian landscape looked different when Steve filed this bug in 2011. Nowadays I'm not sure what's the value of keeping this bug open.