Especially when we're talking about TAS; I can't imagine there'd be nearly as much to add or change in the Encyclopedia from an hour's worth of TAS as from an hour's worth of Enterprise or the new films, so it's not even really fair to compare it hour-by-hour. It's better than it's given credit for, sure, but it's still not exactly dense with information or world-building.
Isn't it? It gave us Kirk's middle name and Amanda's last name. It contains the only onscreen mention of McCoy's daughter. It gave us the name of Kor's starship and introduced us to members of his crew, including the second speaking Klingon female character in Trek history. It established ShiKahr, Vulcan's Forge, the kahs-wan, and the le-matya, and it gave us our first look at Spock's home and his city (and the design of Spock's home inspired the design of T'Pol's family home in ENT, with its walled courtyard connecting to the street and containing a fountain and sculptures). It showed us undisguised Orion males for the first time (though ENT did not follow that precedent) as well as the first sane and articulate Orion female. It gave us Caitians, Edoans, Vendorians, Phylosians, Megans, Aquans, Lactrans, Pandronians, Draymians, and others, and introduced creatures ranging from glommers to sur-snakes to Capellan power-cats. It gave us Carter Winston, Stavos Keniclius, and Robert and Sarah April. It let us see behind the curtain of the "Shore Leave" planet and how it works, the very essence of worldbuilding. It showed us more of the innards of the ship's engineering complex than TOS ever could. It added Starfleet technologies like force-field belts, the bridge intruder-control system, the aquashuttle and scouter gig, xenylon uniforms, and the first holographic rec room, as well as a few new ship classes.
TAS had plenty of worldbuilding and added significantly to TOS's image of Starfleet, the Federation, and the galaxy. And some of what it established has become part of basic Trek lore. Which makes it all the more nonsensical to exclude it from what's supposed to be a comprehensive reference.