The more I think of it, the more I can draw parallel between Bob cassettes and those overpriced DRM-enabled inkjet cartridges, often costing more than the printer itself.
More than two decades ago, this is the first publicly documented attempt at hacking printer DRM - indeed, also accomplished with EEPROMs in the cartridges: https://eddiem.com/photo/CIS/inkchip/chip.html
I thought the GUID was put in the cartridge to prevent the machine from accepting the same one but refilled, since I know this is done with ink cartridges (printer remembers last N cartridge's IDs) so it's odd to see no other mention of that.