I think the concept of stars literally hitting each other is rather moot. As you’ve said, the chances are incredibly tiny… However, a star doesn’t have to literally collide with the sun to cause unfathomable damage and destuction.

A star coming closer than the ort cloud will mess up gravitational interactions, orbits, and rain down rocks/ice from the ort cloud.

I don’t know how much of that is factored into the “they won’t collide so don’t worry” formula/logic though