If the underlying data is constantly changing, how do cursors solve that problem? The only guarantee I get asking for the next page after a given item is that i

If the underlying data is constantly changing, how do cursors solve that problem? The only guarantee I get asking for the next page after a given item is that it won't contain the last item I've already seen. There's no other inherent guarantees. The page could contain all items I've already seen, early pages (in this new version of the underlying dataset) could have items I've never seen, and so on. It's as arbitrary as page numbers but without the corresponding convenience.