Concerning Shields

So, does anyone else think it's odd that Shield Mitigation contiues to rise even after the shields are down? Is there something I'm not entirely getting? Is it a bug? I would think that once shields are down, mitigation should cease to increase. I think this would definitely encourage ships to not focus fire as much, and micro battles if the player wishes so.

If someone could either explain how the shield/shield mitigation system works, or explain if my logic is off or not that would be greatly apprieciated.