Animating graphics while loading were invented as a way to reassure the user that nothing was stalled, halted or crashed. Therefore, any loading graphic whose animation is not directly tied to the thing which is waited on (i.e. the loading of assets, the reticulating of splines, etc.) is fundamentally dishonest, and teaches users to distrust loading animations; that is, the reason they exist in the first place.
Sorry to disappoint you, but historically a majority of progress bars in UI have shown either fake progress or a huge jump between low and high % of completion.