I don't think you should also have to be a C expert, but I am suggesting that, in practice, there is nobody in the world who is proficient in garbage collection who does not also know C. I think if you learned everything needed to understand GC, but were never exposed to C, you would already know enough to pick the language up in a couple of hours.

Nobody is going to turn up in the Go IRC room saying that they have a great idea how to reduce pause times by improving the work-stealing between concurrent markers by using a better lock-free queue algorithm, except do'h they don't know C.

I get your point about just one compiler though - less moving parts is good.