I think it's fair to say that Linux isn't Unix and goes well beyond the design constraints of Unix that were imposed when it was originally started in 1969. That's the era you stick to when you insist on only doing things the Unix way, but there are a lot of other ways to know what your system does and have reliable tools. In current times the most common usage of Linux is Android, which is ostensibly not Unix-like at all regarding its userspace. If you're talking about GNU, that quite literally means "GNU is not Unix".