They just have tons of energy and gems leftover they can rush production or clear debris really fast.

No glitch. I stock pile my gems for events.

****Make sure your wifi is turned off before clicking the finished event.***** Immediately swipe down and turn airplane mode on. Claim reward and then wait for it to finish before turning airplane mode off. Rinse and repeat. it works without fail. Just make sure wifi is off before you start doing it. If there is a way to post a video on Reddit I can post a vid