Gravity blocks does not have a correct and random falling animation visually, but the hitbox looks like are correct and affect strings correctly. It applies to Sand, Gravel, Concrete Powders, Anvils, etc.

For an example, i have made a machine that loops the gravity block with slime blocks to see if it has correct animation or not.

I also visualized the entity hitbox with Lamps so the hitbox can be visualized correctly

Screen recording related to the bug