Yes, this is close to what I'd also prefer to be my definition. "Systems programming" is about writing the programs that users don't care about. This involves all kinds of infrastructure: certainly the kernel, but also various other bits of critical plumbing. But that doesn't fit the definition from that Usenix paper, as nroff was an important user-visible application program, even if it isn't much anymore. I think it is probably best to avoid using the term "systems programming" except when within a constrained community where the intended meaning is clear. Just look at how much confusion arose from the original announcement that Go was a systems programming language!