Hello Sara,
I don't know details about how the developers choose to implement any specific feature in the software, but I expect that making the animation show fully reveresed motion for a fully reversed load instead of animation that shows a zero-based load was just not a high enough priority for the developers. If enough users compliain, it may be put in the list of improvements for a future version. What most users care about is that the calculation of fatigue life was done correctly for both zero-based loading and fully reversed loading.
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