Classic Mac OS stored a great deal of structured data in the resource forks of its files. Those were edited using ResEdit, an essential tool for every advanced user.
ResEdit
Classic Mac OS could give the size of data and resource forks. High Sierra ignored extended attributes, and Sonoma tries to add them, but only includes some.
ResEdit changed what was in the resource fork. With Mac OS X, Apple moved away from forks to extended attributes, now used for quarantine flags and more.
Classic resource forks passed into Mac OS X, but were deprecated by Apple in 10.8. Now in Catalina they can stop working: is this a new security measure?
Do you trust the file size given in Finder’s Get Info dialog? Perhaps you shouldn’t, as it only consider part of the file, its data fork.
One of the great hidden features in macOS, xattrs are rarely used by anyone outside Apple, largely because they are so poorly supported by functions calls and tools.
If you wanted to mess someone’s Mac up, you could go into their system files and change things around when they were out at lunch.
Versioning reflects some of Apple’s worst corporate auntiness. We need more self-determination.
The Eclectic Light Company 