The Crew-10 was not a rescue mission because they just rotated with Crew-9 which carried the Starliner Astronauts back. Crew-9 could be called a rescue mission because they took back the Starliner Astronauts. But Rescue makes it sound more urgent and dedicated than it actually is. They would have flown anyways, just with more crew.
That is exactly what it is. That mission has been scheduled for more than 6 months (though the exact date changed a couple of times for technical reasons).