[janslow]

In most cases, a breaking tooling change should only impact the root project (e.g., they need to change their readme from `go get` to `go install`), so there's only one codebase to fix and it's in the control of the person upgrading the tooling.

Whereas, a breaking language change could impact transitive dependencies of the root project, which a developer doesn't have control over.

[throwaway894345]

Moreover, breaking a language change can result in many changes over any given project including insidious bugs. Breaking the tooling behavior means you have to update your build script and your workflow. Meh.