The functionality we're discussing can be used for tools that are not build dependencies. They may be important for your project and worth having contributors be on the same version but not part of the build.
It will still add the dependencies of those tools as indirect dependencies to your go.mod file, that is what's being discussed.
If you use the tool to develop your project then it is basically a build dependency. That is a sweeping generalization, but it's essentially correct in most cases.
It will still add the dependencies of those tools as indirect dependencies to your go.mod file, that is what's being discussed.