The major roadblocks for WasmGC in Golang at the moment are (A) Go expects a non-moving GC which WasmGC is not obligated to provide; and (B) WasmGC does not support interior pointers, which Go requires.
These are no different than the issues you'd have in any language that compiles to WasmGC, because the new GC'd types are (AIUI) completely unrelated to the linear "heap" of ordinary WASM - they are pointed to via separate "reference" types that are not 'pointers' as normally understood. That whole part of the backend has to be reworked anyway, no matter what your source language is.
Go exposes raw pointers to the programmer, so from your description i think those semantics are too rudimentary to implement Go's semantics, there would need to be a WasmGC 2.0 to make this work.
It sounds like it would be a great fit for e.g. Lua though.
That's not the base language, it's an unsafe superset. There's no reason why a Wasm-GC backend for Golang should be expected to support that by default.
If it is part of the language reference it is part of the language.
Usually when language reference books used to be printed, or we used ISO languages, what is there on paper, is the language.
We are only discussing semantics, if it is hardcoded primitives, or made available via the standard library, specially in case of blessed packages like unsafe which aren't fully implemented, rather magical types for the compiler.
Which is nothing new since the 1960's that there are systems languages with some way to mark code unsafe, the C linage of languages are the ones that decided to ignore this approach.
The standard library uses unsafe for syscalls, for higher-performance primitives like strings.Builder, etc, so it's support is mandatory to run any non-trivial Go program
For a while the GOOS=nacl port and the Google App Engine ports of Go disallowed unsafe pointer manipulation too, so there is some precedent. Throughout some of the ecosystem you can see pieces of "nounsafe" build tag support (e.g. in easyjson).
Somehow I don't think Wasm-GC is going to support bare metal syscalls anytime soon. That stuff all has to be rewritten anyway if you want to target WASM.