What do they mean by "surprising depth"? What's a good example of "surprising depth"?
My DD12 is older than your situation, but here's what came to my mind when reading this question:
1 - For her 6th grade gifted glass, the students were supposed to complete a project and present on it. Some kids did science experiments, some wrote a story, etc. She decided that, since she had played classical and blues music on piano, that she wanted to study jazz. She learned the history, learned about polyrhythms, syncopation, etc., and recruited the instructors at her music school to join in recording a piece she wrote herself.
2 - For her 5th grade science fair, she remembered her mom (with a Chemistry degree) describing chromatography. Rather than creating a poster describing it, she insisted that we buy a paper chromatography kit and analyzed the dyes used in M&M candies, after researching the techniques and science. (One judge, a local college Professor, wrote on the judging form "this kid should) be in college")