This is not a bug, it is intentional and I know it. This was added around 1.4.x.

So you can't directly move a block entity, since it has a NBT (inventory etc.). Simply by making block entities `Moveable` this can be done easily, but block might (would) destroy it's inventory. Instead of just making it `Moveable` maybe do it `MoveableBlockEntity`, piston checks the block, stores NBT if it is a `MoveableBlockEntity` in itself (or somewhere else), then puts it back when block is stable.

I know this might affect the performance since there might be a lot of NBT copying happening, but this is already implemented in bedrock, and people already implemented this as a mod (https://github.com/gnembon/fabric-carpet this mod contains it), and it looks stable.

This would be really cool as a feature.