I don't ever agree with this. You end up using only the (minimal) features that they all support. I can't imagine going from PostgreSQL features to MySQL.
And you should always dev/test/stage on the same database that you'll use in production.
Everything you're saying is true, but if the devs can run unit tests on sqlite, that's a big win. And you shouldn't discount this feature off hand, or limit yourself from being able to do this.
It's one thing if you want to run postgres locally, that's fine, but who really wants to run Oracle on their laptop just to run unit tests, or to test an api locally?
And you should always dev/test/stage on the same database that you'll use in production.