When you make a gravity block fall and then tp the falling block to an area, the hitbox of the falling block entity will be teleported, but the model will stay in the same place it was before being teleported. The model will also still fall but will not break or turn into its block form when lands on a block. when the hitbox lands on a block, the model of the falling block will go to the hitbox, making it look like it teleported.

Steps to reproduce:

• Place a command block in the sky, then add this command: 

/tp @e[type=falling_block] ~ ~-2 ~

• place a button on the command block, then place a gravity affected block.
• when the falling block falls, press the button. the falling block should still be falling in the same place it was before.

What is supposed to happen:

The falling block should be teleported with the hitbox of the falling block.

in some cases, this will happen with falling blocks on a piston.