Are you talking about the "Blatantly off-topic" reason? That is shown to people without the close vote privilege who are flagging to close a question.
An example from Engineering SE where I don't have enough rep to vote to close, reached by flagging the post, then selecting should be closed... > off-topic because... :
From Shog9's answer on the Q&A on MSE: No custom off topic message when flagging on SO:
There's no good reason to allow entering a custom message here though; they'll still require a person with close vote privileges to close them, and the reason should be obvious to anyone reviewing the flag.
Since you have 3K rep here, you can now cast close votes, so you won't see this option any more. Instead, you're supposed to either choose one of the canned reasons, or select off-topic because... > Other... from the close dialog and add an explanation of what's wrong with the question.