Since we have this rule very clear in our help center that questions asking for datasets are off-topic, could we include this reason in the off-topic dialog?
The initial suggestion would be to include the current text in the help center and a link to it:
Questions about obtaining particular datasets are off-topic, because they are too specialized.
Possible advantages:
Currently, I flag such questions for 'moderator attention', but with a customized reason in the off-topic dialog the community would be able to help in a more automatic way. Please, advise me if I should be using another type of flag for this.
A second advantage would be to spare comments explaining to the OP why the question is off-topic.