If you see your Acropora exhibiting these strange behavior, do not panic. They may simply be spawning! Acropora spawn at night and are queued by seasonal environmental changes – changes that reefkeepers can simulate using moon cycles and seasonal temperature programs. The first video was likely taken after-hours (evidenced by the nighttime behavior of the Damselfish which makes a cameo); The owner may have turned on his lights to document the incredible mass broadcasting of Acropora eggs. If you look carefully, you can see polyps releasing eggs into the water.
Interestingly, both videos (from different reefkeepers) come to us from France, a land known for wine. Coincidence?