Sqlite isn't something that works for only apple or google. Point is it's sufficient for them, simple, and more than sufficient for you. He's explaining to you that this is something that has already happened as you're unaware.
I use SQLite all the time, I said in another comment it's my go-to for server-side green field projects. But there's a lot of push to create data solutions that are fully bidirectional between client and server, or to even make them client-driven in an awkward peer-to-peer model, and I'm not sold on either pattern.
Sqlite is at it's best in "pure client" situations where there is no server and there are no P2P things going on. Just the application, the user, and their data on their own drive with sqlite.
My concern is over-reliance on client side storage and the complexity it adds to have records of state on both client and server.