Even if they decide to bring the Starliner crew back with a Dragon they will have a short time period ( few hours/days ) where there is no possibility to evacuate all ISS Crew in case of an emergency. The Starliner has to undock before the arrival of the Dragon ( Crew 9 ) to free the docking port. Or is it possible for Dragon to dock at one of the ports blocked right now by the various cargo capsules, which then have to be undocked first?
skadi