Terror's Lair was technically not designed as an introductory adventure. It was a solo adventure, following a very predetermined path, with the main objective to show a player or refree how the game system worked. It could be redesigned by the referee to a conventional adventure, but would have needed some work.
The Tricolor's Shadow in the 1st edition Traveller: 2300 was more of an introductory adventure, even if sparse, and it highlighted a problem that followed the game from the beginning. Information about the 2300 universe was sparse, even warranting the publication of Understanding 2300 that was included in later boxes of the 1st edition. It also locked the demonstration of new settings and game themes into a broad metaplot leading up to Invasion.
That is why I think that 2320 AD is not only a good update for us old timers, but the book also makes much easier for beginners, as they can start playing with a full universe.
Even so, an introductory adventure is useful, or perhaps even just two or three adventure seeds showing distinct ways of how the 2320 AD universe can be used.