The grumpy snarky HN user in me says that a lot of the "I deployed a server to do X" and "I wrote code to do Y" in this blog post should actually say "A Facebook engineer provided me with direct API hooks to do X and Y", but it's anyone's guess.
To use an existing private service, not nearly as much effort.
That being said: Of course he could have learned how to train a model himself, but even in that case he is using training infrastructure and data that is available to him that is not public. I highly doubt he had the time to build those sorts of things himself. But his goal was more talking to his home and using tools to build an interactive home assistant. Sounds like he was very successful at doing that. He wasn't out to build the individual AI pieces, doesn't make it not cool or interesting.