When Mac users update to macOS Ventura and later, there is a new feature in the Photos app called Duplicates Album. This album automatically appears in the sidebar when it detects duplicate photos in the library. You can open the Duplicates album to manage the duplicate items.
However, this feature doesn't always work well. Some Mac users encounter the problem that the Ventura Photos Duplicates not showing, and some find the Mac Photos finds duplicates incorrectly. If the Photos thinks some items are duplicates but they are not, you can't mark the item or tell Photos that it is not a duplicate.
You should know that this new feature just automatically finds duplicate photos in the Library, but it won't automatically merge or delete the duplicates. To delete duplicate photos on Mac needs extra steps. Therefore, even if there is no such an "Ignore" button, you can just leave the incorrect duplicates alone, it has no impact on the photos.