U.S. Statement on Reliability of Election Results
nytimes.com
nytimes.com
If we have a credible reason to think Russia is unilaterally attacking our infrastructure in a way we don't do to other nations (e.g. reading tapping their president's phone) then please provide the evidence to the public straight up. Otherwise, don't insinuate.
The reason they won't let reporters attribute statements to them is because while what they are saying is true it's not the official stance of the organization and/or the guidance documents they work off havn't been updated to include those statements.
"evidence" is beyond the scope of the interaction unless there is some reason to question the integrity of the spokesperson.