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Yes, this is covered in the video. He talks about use in antiquity and in modern buildings.

https://www.youtube.com/watch?v=y9-p4AkgVU8&t=407s

The author acknowledges present use and also gives intriguing historical examples from Vitruvius and and Da Vinci.

An acoustic jar, also known by the Greek name echea (ηχεία, literally echoers), or sounding vases, are ceramic vessels found set into the walls, ceilings, and sometimes floors, of medieval churches. They are believed to have been intended to improve the sound of singing, and to have been inspired by the theories of Vitruvius.

https://en.wikipedia.org/wiki/Acoustic_jar

I've seen the top picture installed in a few places, and always wondered what their function was.

Learn something new every day, and this time it was 10 minutes after I woke up! Thanks!