Actually they do have incremental compilation at the package level. Use go install and you'll get it. Use go build and you throw away intermediate build artifacts so you don't get it. This is all documented.
In practice compilation times are not a pain point for golang.
their wording was confusing; they were being sarcastic, implying that the go developers made compilation of a project from scratch so fast because they weren't aware of incremental compilation (which is a false assertion, I assure you).
In practice compilation times are not a pain point for golang.