There are different opinion about the subject. Some says that the leaves are praying when there is to much light , some says that it is because the plants are healthy and happy but I remember that a long time ago I have read an article about it and it was linked to the plant sweating : to keep more water and avoid sweating they are doing that and the opposite when they want to sweat but I am not 100% sure about it as it was a long time ago. And last thing it could also be because of a light too high so the plant is trying to reach it , you will have a different answer from each growers 😊👍