such pedantry
if I "update" any file, than windows deletes the old copy & writes a new one.
So I don't understand your last post, sorry.
If I update some text in a book ( e.g. I change one letter of one word in one line ) - then save the update, that means - to the operating system - write what's in RAM to disc & delete previous version.
doesn't really matter whether that "book" is an epub(zip) or a word doc, or a text file ?