Originally Posted by chadteck

This actually makes sense. It's fairly obvious that the frame is subjected to more stress on the trainer since the bike is constrained from tilting side to side. It doesn't matter that the lateral position of the wheel doesn't change on the road, it matters that the wheel (and frame) are allowed to tilt freely.

The point about the wheel being allowed to absorb some flex is good as well.

Nobody is claiming that a bike on the road isn't subjected to stress. I think the point is that the frame is probably subjected to considerably more stress while in the trainer.