Falling blocks (gravel, sand, anvils, etc.) have a tendency to suffer a momentary visual desync when their motion is changed by an external force. Moving falling blocks with bubble columns, slime block launchers, fishing rods, explosions, or modifying the Motion: tag via commands all produce a momentary visual stutter - some cases more severe than others - in which the affected block appears to travel further along its original trajectory (or stop altogether, in some cases) before updating to its new position and motion.
And, for whatever it's worth, this does not seem to affect TNT entities, or falling_block entities attached as passengers to another entity.
See attached videos for examples.