Hello Robert
External routes are defined as routes learned by an EIGRP process via redistribution. This redistribution can also take place from one EIGRP AS to another just like in the lesson. In the lesson, you can see that these routes are marked with the EX designation, meaning they are indeed external routes.
This behaviour of choosing the lower EIGRP AS as better takes place only when you have multiple AS’es configured within your EIGRP topology, and when the same route is learned from two different EIGRP AS processes.
Now when you say “internal routes, from two different internal AS processes” I’m not sure what you mean. All routes that are “internal” to a router, are those that are directly connected. Those are not learned via EIGRP, but are automatically placed within the routing table. All routes learned via EIGRP are learned from other routers. So you never have any “internal” routes learned via EIGRP.
I hope this has been helpful!
Laz