I've been interested in this idea that he cut an iPad up with a knife.
I have an iPad. It's aluminum and glass. You don't cut either of those with a knife.
If I had to guess, I'd say he used the knife to pry it open in the hopes of removing whatever it uses for data storage, although it may not have been immediately obvious to him once he got it opened, if he did, which thing inside there is used for data storage.
As I understand it, the iPad uses some kind of flash RAM and not a hard drive, and if you aren't familiar with which chip maker produces what kind of chips and some of the nomenclature silkscreened onto the packages, one Integrated Circuit looks pretty much the same as any other.