I think it's an artistic expression, obviously, after the smoke clears, their bodies are basically intact except for the flecks.If normal shells were used instead of 6000 degrees sabot, they would certainly not be able to do this.
Star Upper's biggest special move. Star Upper's punches are delivered with such tremendous speed that they are close to the speed of light. The apparent mass (the size of the fist) is then infinitely close to the maximum according to the theory of relativity, resulting in unimaginable destructive power!
At a depth of 18,000 feet, the pressure exceeds 5 tons per square inch, which is more than even the force exerted by the Devastator (6,000 pounds per square inch, which is enough to demolish an entire skyscraper).