Whataboutism is a fallacy when being used to dismiss the argument entirely. It is not a fallacy when used to state that the reason other problems are dismissed

Whataboutism is a fallacy when being used to dismiss the argument entirely. It is not a fallacy when used to state that the reason other problems are dismissed should also apply here. The difference is: Fallacy: "What about Y. X isn't a big deal as long as Y is an issue." Not Fallacy: "What about Y. Y isn't a big deal because A, B, and C. A, B, and C also apply to X, so shouldn't that mean X isn't an issue as well." The problem comes in that the second sentence in each scenario is left shortened if not completely left out, making it hard to tell which version of 'What about' a person is using.