The Go team at Google would run a collection server. Each week, with 10% probability (averaging ~5 times per year) the user’s Go installation would download a “collection configuration” to find out which counter values are of interest to the server and at what sample rate. If there's interest to use config files to determine how telemetry is done, why can't similar be done about turning telemetry off? I don't want to…
As designed, the system allows an opt-out _either_ by setting GOTELEMETRY=off in your environment or by running 'go env -w GOTELEMETRY=off' which writes a config file. (Specifically the one reported by 'go env GOENV'.) If you prefer to edit the config file directly, you are of course welcome to do that.
Thing that work inside the Googleplex often don't work for the rest of us. Not every company is a multi-billion-dollar behemoth that can afford to spend hundreds of millions of dollars annually to work exclusively on internal developer-tooling.