Earlier quoted context omitted.
How? The telemetry is still only present in the toolchain. A library would be imported and built, and could trigger the telemetry collection, sure, but in what way would that be considered "part of their code". If another developer is using their library, then it would ostensibly be a go developer who themselves has chosen to opt in or out of the telemetry, so they wouldn't be pushing it onto their users either.
If there are a wide variety of well-maintained libraries available in Go, people are more likely to pick Go, or even feel compelled to choose it, and possibly be subject to telemetry. If the bulk of developers cease to create or maintain Go libraries, fewer people will use Go and be subject to its telemetry.
Your argument is that one user publishing a library in a sea of libraries which enriches the ecosystem is equivalent to directly pushing telemetry onto their users.... Because people are enticed by golang as a whole?
One library isn't going to be the deciding factor in someone choosing a language, and they'll likely have to deal with telemetry well before they get to a random library.
And that still doesn't answer the question on how that possibly means telemetry gets injected into their code.