go mod started out with a bunch of flags, and was only later converted to the current syntax:
https://github.com/golang/go/commit/6121987a10b2c54bc4c48473...From the commit message:
> We've avoided subcommands in the go command to date, and we should continue to avoid adding them unless it really makes the experience significantly better. In this case, it does.
So, I don’t see it as a contradiction to the mail you’re quoting :)