defer is no worse than Java's try-with-resources. Neither is true RAII, because in both cases you, the caller, need to remember to write the wordy form ("try (...) {" or "defer ...") instead of the plain form ("..."), which will still compile but silently do the wrong thing.
Sure, true RAII would be improvement over both, but the author's point is that Java is an improvement over Go, because the resource acquisition is lexical scoped, not function-scoped. Imagine if Java's `try (...) { }` didn't clear the resource when the try block ends, but rather when the wrapping method returns. That's how Go's defer works.
Can't you create a new block scope in Go? If not, I agree. If so, just do that if you want lexical scoping?