how do you know those queries are actually correct without domain knowledge?

Do you know enough about JOINs and how they work to be able to break those big queries down and figure out whether they are doing exactly what you're asking for in English?

You don't, and if businesses start using vibed reports for regulated reporting then I guess we'll see soon what the courts say about that

You don’t. But you can still check ? ¯\_(ツ)_/¯