That encyclopedia is a real piece of ... very hard to compare anything or even find what you want. On top of that it's laggy as hell (for a simple HTML/pdf document).

For me, the easiest way to find what each level of barracks can train (in addition to the lower level barracks) is to hover over the barracks building in the research tree. It shows, what additional units the barracks give. This does not seem to be an exclusive list though. I guess, just the very top level additional units are shown.

As a tip, whenever you conquer an enemy territory and they have some military buildings there check what you can recruit. They might provide units that are not available to you at that point (or at all) even though the icon in the city interface shows that you cannot use the foreign barracks. Actually, you can train units there. In my Egypt campaign, some barbarian high level barracks were giving me thorax pikemen and royal peltasts before I could train them myself.