Consider that one of the challenges to early Photoshop was be doing graphics manipulation that is right at the edge of what the hardware at the time is capable of, I don't think that stuffing a relational database engine between the raw bits and the drive would be helpful.

The challenge needs to add the condition of the app stretching the hardware capabilities so hard that a whole pile of not-so-clean optimization tricks are necessary to get the performance up to the acceptable level.

SQLite versions 1, 2 and 3 have completely different file formats as well as differing semantics especially around typing. Later versions cannot even read earlier versions.

The file format is also well documented and fairly complex. https://www.sqlite.org/fileformat.html

Considering SQLite is only 15 years old and implements a rigorous specification instead of an evolving set of product requirements, you're just over halfway to what he talked about.