From what I can tell, it's the invocation model and deployment that is unique here?

You invoke faast from your local machine (or build server, or cron job, whatever), and in turn it deploys some functions to a serverless platform and runs them, then tears them all down when complete. Eg, from the site, this code runs locally:

    import { faast } from "faastjs";
    import * as funcs from "./functions";

    (async () => {
        const m = await faast("aws", funcs);
        try {
            // m.functions.hello: string => Promise<string>
            const result = await m.functions.hello("world");
            console.log(result);
        } finally {
            await m.cleanup();
        }
    })();

You wouldn't want to run this code on serverless, as you'd be paying for compute time of just waiting for all the other tasks to complete.

It would be useful to see a discussion about how and where to host this entry code, may even a topic on "Running in production".

It's definitely a neat idea because if you control the event that kicks everything off anyway (eg: "create monthly invoices" or "build daily reports") you can deploy the latest version of everything, run it and clean it up in essentially a single step.

(Please correct me if I've misunderstood any of the details here!)