What the fuck is "UMD Core?"
UMD core, or PSP core, are movies, or games, that would thanks to the demographic have a UMD movie made for them. The Sony PSP had a special disc format - the UMD - which was a tiny disk inside a plastic caddy that you could stick into a PSP. Along with games they also had: video. This was before the era of streaming video more or less (I did download videos from Google Video and stick them on my PSP for later viewing and it felt really cool)
So yeah think...Middle Class Dudes between 12-22ish circa mid 00's who were into Korn and Adult Swim.
Stealth was a CGI film about a stealth fighter jet that was not particularly good, and the Stealth UMD contained a demo for wipeout pure, itself a PSP game. But in the demo, you could fly the airplane from Stealth as a ship. This was the only way to do so.
So having a UMD of a very forgettable movie with a tie-in demo for a game on the same system...that's PSP core baby.