The indictment[1] sheds some light on the difference: "On or about December 11,2015, he downloaded approximately 14,000 files from SVN. These files contained critical engineering information about the hardware used on Project Chauffeur self-driving vehicles, including schematics for the printed circuit boards used in various custom LiDAR products."

In other words, the accusation is that he stole technology that was the output of the entire Project Chauffeur team, not simply stuff of his own creation. Presumably, those materials were non-trivial and represent the combined effort of many engineers over many years.

Imagine you're toiling on a team for years and your absurdly compensated boss decides they want the whole pie, clones the repo their laptop, and dips out to found their own start up based on everyone's work.

[1] https://www.justice.gov/usao-ndca/press-release/file/1197991...