AI does mean something, but it’s quite disappointing.
Even mundane algorithms like A* pathfinding are technically under the umbrella of Artificial Intelligence. However the public’s perception of what AI means constantly shifts to be “whatever computers can’t do today”.
They’re not stranded because the part of the capsule that isn’t working has multiple redundancy and is intended to burn up on reentry anyway.
Starliner is perfectly capable of leaving the ISS whenever they want, but they would be unable to continue collecting data on the thruster shutoff (again, because it would burn up in the atmosphere).