I mean this is more of less what using a local container for Postgres is. It’s not exactly one file but it’s hidden in a volume somewhere where you don’t need to go file digging, so for all intents and purposes sure, it’s one file.

Most ORMs also will let you swap out your RDBMS so you can run sqlite locally and Postgres in prod via the same code. I think this is a bit of an anti pattern though. While the two are similar in most standard use cases, it’s not always apparent when you veer off that standard use case and into something that’s not supported by sqlite. And then all of the sudden you either have a divergence between what works locally vs in production or you start to intentionally limit your app’s capability to only what works with sqlite because you can’t locally validate it.