For agents in the wrong country at the time of the announcement, it may just condemn them to torture or death.
These are agents who have materially harmed another nation, it isn't as if they have only been acting in a purely defensive capacity and working on the internal security of the US.
You raise a point that they weren't acting in a purely defensive capacity - for all we know, "did Russia harm" could mean they were a counterintelligence agent that successfully sounded the alarm on a Russian intelligence operation on US soil. From that perspective, wouldn't Russia be the aggressor now?