@bullivant I read that as a marketing statement for Duolingo investors. It's saying that this isn't an app with an addressable market of people learning a language. Rather it's "AI" with the purpose of replacing teachers with lower paid workers and the addressable market is primary and secondary education world-wide.
It's long been a play of the tech bros to make the addressable market near-infinite. That makes the VC firm's spreadsheets look very rosy. Musk in particular is good at this: the addressable market isn't luxury car buyers, but all of transport because those cars will be autonomous and will be able to be leased as taxis when unneeded by their owners; we're not just building rockets, with all that downside risk, we're going to own a whole planet!