Sand turns back and forth from a block to an entity on top of moving pistons

The bug

When sand falls on very quickly moving pistons, it is continuously turned into a block and back into an entity again. This allows for plants that are placed on that block to grow very quickly (see MC-113809 and MC-165023)

To reproduce

Build the contraption from this video by [Mod] violine1101: https://youtu.be/TPklP6WZrLk

Video

Video by Ray showcasing a farm that can be built using this bug: https://youtu.be/mg93ldmI584