This reminds me of how I used to cheat at certain games back in the 8-bit olden days. You could change one thing at a time, save, then look through and see what changed on the disk. Eventually you could identify all the locations that held the values for inventory, stats, location, quest stages, NPC state, and so on. All you had to do after that was change those locations and - hopefully - you're all powered up. With the WozMon you could even find the locations in memory, sometimes, and have "free" healing spells, for instance, any time you like by popping open the monitor and just changing the values in RAM. Among people my age this is the usual way you'd get started with something resembling hacking. It seems like the author is doing the same type of thing. This is also the basis of cheats and trainers for games, action games tended to be easier and there might only be a handful of flags and variables making cheat menus practical. For RPGs the cheats came in the form of lists of locations on the disk, eventually though there were disk-based full blown character editors available for some handful of games. Also about the same time, some developers started to go to extreme lengths to keep people from cheating by tampering with their save game files. This became quite common in the industry by the 32-bit era.

EDIT: I will point out that people would often submit letters to computer magazines with the memory locations of popular games as time went on. But this could take months or a year or more, and a game might never have its secrets laid bare so I suspect a LOT of people just did it manually at home.