I suspect it's more at a program level. Boeing have lost a lot of money on Starliner, may lose a lot more, and already seem lukewarm on continuing with the project. It's actually NASA that's keener on keeping it running, so that they are not entirely dependent on SpaceX for human spaceflight.
That doesn't seem right. It's supposed to be up there through to 2030+, and the point of a 2nd supplier is just to ensure there aren't any blocker level problems if a single supplier has issues.
