You're right that POSIX doesn't specify syscall tables.
What I wanted to point out is that Go also supports BSDs and other kernels out of the box that implement the POSIX standard, though with slightly different syscall tables and binary formats on those target platforms and architectures.
I was referring to POSIX as a standard specification, because it also includes not only Linux's syscall table, but also various other things that you can typically find in the binutils or coreutils package, which Go's stdlib relies on. See [2.1.3] and following pages.
I guess what I wanted to say: If I would bet on long term maintenance, I would bet on POSIX compatibility, and not on one specific implementation of it.
