How is the bolded section any less a violation of the conservation of matter than what the Hulk does?
It’s clear that our laws of physics don’t apply to super-hero universes. The only super-hero character I can think of who comes close to obeying the laws of physics is Babs Gordon/Oracle.
It gets worse when people try to answer these kinds of questions - I remember there was a character in the Wild Cards universe - Elephant Girl or some such. When she turned into an elephant, it would cause massive blackouts from the energy that she converted into mass; when she turned back, there would be a big flash of light.
Both effects are nothing close to the energy that would be required to create 5,000 pounds of mass. “Leaves a smoking crater about 500 miles wide in the Earth’s crust” is closer.