I think what the author was trying to figure out was not just when you should do a major/minor version update, but how that could be done automatically. An example is how in Elm it can detect a major vs minor change and bump your numbers automatically when you publish. Something like that for Go could be built into some tool to help package maintainers (public + private) keep SemVar up to date automatically since there are already types and there are ways to possibly detect changes since a previous version.

I imagine you could write a tool that would check the previous highest "v*" tag in git's version of the project vs now using something like go-guru and determine if any public interfaces were changed and that could automatically determine if it's a major or minor bump.