While I guess you could say that a "fake" registration, is a registration, but with it you can use your device without actually registering. If you zero out the database "user" entry, nothing is registered with anybody.
I don't use the Kobo stock software to sync or read ebooks, so I can't tell you what not registering with Kobo disables. I don't use "collections". The readers I use don't use a database to manage my ebooks, they use a normal File Manager to select the ebook files. I can, of course, use the search functions to get lists of books that match the search criteria, and select books from those lists.
Luck;
Ken
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