Specific companies policies might need to have a common home page set for all users and currently, a confluence user personal setting will overwrite the global home page as stated in the documentation.

Confluence admin should have a setting to "force" the global home page over user settings.

workaround

I could create this query that will show all users that have a home page set instead of using the global home page:

SELECT um.username, os.entity_key, os.string_val FROM OS_PROPERTYENTRY os
JOIN user_mapping um on um.user_key = trim('USERPROPS-' FROM os.entity_name)
WHERE os.entity_key = 'confluence.user.site.homepage';

and this delete sql will remove their setting leaving only the global home page setting.

DELETE FROM os_propertyentry WHERE entity_key = 'confluence.user.site.homepage';

Remember, always perform a full backup of the database before performing any update or delete query on it.