Hello,
J-Novel Club receives requests to correct errors found in published ebooks. When time permits ebooks do get updated.
That is why you may be seeing Bookworm volumes in the updated field of your library.
A fellow user has put together a change log for those updates, https://forums.j-novel.club/topic/6286/epub-update-summary-nov-2022
Normally, most updates are minor with few changes.
Thank you