Don't know what he wanted to talk about, but here's one I remembered off hand:
https://en.wikipedia.org/wiki/Z-machine
All the old Infocom games were ported to this Engine and its existence is why they're so wonderfully well preserved nowadays and can be played in a really playable form with Frotz

Also in the Adventure Game space:

https://en.wikipedia.org/wiki/SCUMM

The oriignal MUD was an engine, and there are hundreds of derivatives of MUD that are also engines, I recommend Richard Bartle's book for a really good history of it, I think it's free online.

https://en.wikipedia.org/wiki/Multi-user_dungeon#Wider_acces...

https://mud.co.uk/richard/DesigningVirtualWorlds.pdf

Bartle's own words:

> MUD was programmed in MACRO-10 assembler on a
DecSystem-10 mainframe at Essex University, England, in the
fall of 1978. Its author was a talented Computer Science
undergraduate, Roy Trubshaw. Version I was a simple test
program to establish the basic principles by which a shared
world could be maintained. When it worked, Roy immediately
started on version II, a text-based virtual world that would be instantly recognizable as such even today. It was also written in MACRO-10, a decision that led to its becoming increasingly unwieldy as more and more features were added. Because of this, in the fall of 1979 Roy made the decision to begin work on version III of the game. He split it in two: The game engine was written in BCPL (the fore-runner of C); the game world was written in a language of his own devising, MUDDL (Multi-User Dungeon Definition Language). The idea was that multiple worlds could be constructed in UDDL but would run on the same, unmodified engine (which was effectively an interpreter).

Not only is it clearly the same content generation process as modern engines, he even called it an engine. (this book is from 2005 IIRC but I think it's mostly a moot point what they're named)

PLATO:
> There had been graphical virtual worlds before.
The seminal PLATO (Programmed Logic for Automatic
Teaching Operations) system went live at the University of
Illinois way back in 1961, and many games were written to take
advantage of both its network connectivity and graphics-
capable plasma display units. Some of these laid down principles
that would greatly influence the development of later computer
games; some came close to being virtual worlds; some actually
were virtual worlds.
Orthanc, by Paul Resch, Larry Kemp, and Eric Hagstrom, was an
overhead-view graphical game that, although not implementing
a shared world, nevertheless allowed communication between
individual players. It was written as early as 1973. Jim
Schwaiger’s 1977 game Oubliette (inspired by Dungeons &
Dragons and Chuck Miller’s earlier multiplayer game, Mines of
Moria) had a first-person point of view and used line graphics to
render the scene ahead. It had persistent characters, but was
not a persistent world. Also, the interaction it allowed between
characters was very limited; it was almost there, but not quite.
In late 1979, the first ever fully-functional graphical virtual
world was released: Avatar. Written by a group of students to
out-do Oubliette, it was to become the most successful PLATO
game ever—it accounted for 6% of all the hours spent on the
system between September 1978 and May 198517. Again using a
Fantasy setting, it introduced the concept of spawning to
repopulate areas automatically after players killed all the
monsters.