Steps to reproduce:
1. Create a new site "My Site".
2. Enable Local Live for site My Site.
3. Add Page "Page A" with a subpage "Page B".
4. Go to Site Pages > Click Staging > Publish to Live.
5. Under the pages panel, click Change and then in the dialog click Change Selection.
6. In the page tree, uncheck Page A and check Page B.
7. Click the Change link in the Pages panel again and make sure that the table contains Page B and the option Include Ancestor Pages is disabled.
8. Close the dialog and click Publish to Live.
9. Go to the Live version of My Site.
Notice that despite having Include Ancestor Pages disabled, Page A (ancestor of Page B) has been published, too. Ancestor pages are always exported/published to prevent errors. Thus, this option is not necessary.