Exactly. I'd argue that the majority of people complaining about Go being unusable for them because of the GC would actually be able to deal with the GC easily. I'm working on a soft realtime application in Go, and the GC has never gotten in the way.
Right back at you though: I'd argue that the majority of people complaining about OCaml (or even the JVM) being unusable for them (and using Go instead) would actually be able to deal with it easily.
It is relevant though. You're talking about the large number of people who are using C and don't need no GC as though they're people who should be using go - but if they don't need no GC they probably don't need a language as low-level as go full stop and would be better served by a more expressive alternative. Ultimately, a large proportion of "people who need go or C" actually need C, making this library a good idea.