They were not “passing the time” (more than people on ISS always are… 🤡).

The decision was made in August that they would join the Expedition 71/72 crew.

As a result, Stephanie Wilson and Zena Cardman did not get to fly on Crew-9.

Yes they could go back to Earth in case of an emergency and would have to take the other passengers with them prior to the end of their missions.

It would have been prior to the end of their own missions as well, since they became members of Expedition 72.

They couldn’t not return to Earth simply because they decided they wanted to go back.

Do you think astronauts ever go to space with the expectation that they can “return to Earth simply because they decided they wanted to go back”? 😂