I'll dare try this;
Is your question why is Flash/Animate worse then AE for motion graphics?
For a simple animation as you've shown I'd presume Flash/Animate would be more then capable of doing this. To recreate this in AE might be more work then needed for such a small effect.
Flash/Animate vs AE are two different beasts, yes they both animate but they generally target two different environments. As with any program over time it usually gets better and debuts more tools so give it time.
you'll probably want to look at using tweens and easing in order to make the animation similar to the one shown. I personally would make each fingerprint "line" its own layer and control it that way.
Hope this helps some.