score:4
This custom occurs on a few of the Ionian islands such as Corfu (and Zakinthos). In Corfu it usually occurs on holy Saturday where they toss ceramic pots off their balconies into the streets.
As you know the video link is mistitled. This is not the holy Saturday night/Midnite Anastasis service, this is Great Friday evening of The Epitafios Lamentation service. Some say these traditions originated with the Venetian rule after the defeat of the Ottomon seige, others say they are of pagan origins.
Regardless this custom is meant to symbolize the Harrowing of Hades or more specifically the smashing of the Gates of Hades, where Christ burst through the gates and released the captive souls. St Macarius gives a homily on the descent into Hades with a twist where one can make the connection of this event and the smashing of pottery. St Macarius states (source):
When you hear that the Lord in the old days delivered the souls from hell, how He descended into hell performing that glorious deed, do not think that all these events are far from your soul. The same Lord comes into the souls that seek Him, into the depth of the heart’s hell, and there commands death, saying: ‘Release the imprisoned souls which have sought Me and which you hold by force’. And He shatters the heavy stones weighing on the soul, opens graves, raises the true dead from death, brings the imprisoned soul from the dark prison… Is it difficult for God to enter death and, even more, into the depth of the heart and to call out dead Adam from there?