Hi @Shane Siegfried,
I'm sure that SharePoint Online search results only show content that a user has permission to see. Is it possible for users to obtain permissions in other ways besides what you grant in your organization? You can have a test, for example, there is a file A which the user shouldn't have access but shown in the search result. Check the permissions user has to file A via Manage Access >> Advanced settings >> Check Permissions.
If the user has other permissions to the file, someone else in your organization must have given him the permissions.
If the answer is helpful, please click "Accept as Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.