Yes. OpenBSD famously has an official policy of not providing binary compatibility. You can always break userspace for the benefits of code quality and safety.

Yes. OpenBSD famously has an official policy of not providing binary compatibility. You can always break userspace for the benefits of code quality and safety. ABI has changed? No big deal, just recompile. Furthermore, since OpenBSD is an entire operating system, not just a kernel, the project has power to apply technical decisions to userspace, so you have more control to do that at will.