Looks like any Power BI App shared with the Entire Org is visiable to the External Users once signed up to view the first App. By clikcing on App then Get More Apps they can see all Apps Shared Inte...
rayishome
Resolver I
Resolver II opened a ticket as suggested and spoke with a Support Engineer. It looks like it's working as Designed treating anyone that shows up in the AD User List, Guest or not, as Internal allowing them access to App's published to the Entire Org.