I could imagine national security reasons for not saying specifically where one believes the laptop to have come from, but why would the campaign be prevented from simply saying that the emails are fake and that the meeting definitively did not happen?
Saying the emails are fake would be a direct acknowledgment of the incident that the agency is trying to investigate. This is similar to the “Glomar Response”. https://en.m.wikipedia.org/wiki/Glomar_response.
Well, hypothetically, it could be that the CIA or NSA was spreading misinformation, then tracking its spread, to detect where leaks/spies were. That seems highly unlikely in this case.
