func main() {
    var args struct {
        One string `required:""`
    }

    kong.Parse(&args)
}

Outputs:

Usage: test --one=STRING [flags]

Flags:
  -h, --help          Show context-sensitive help.
      --one=STRING

I would expect that Kong would not print the trailing [flags], since there are no other expected flags. I believe this is happening because the --help flag is optional and considered when deciding to print out the [flags] summary:

It's minor, but it feels like it's implying there are other flags, when there aren't.