I think they're suggesting that bad latency from a serverless architecture is mitigated by a SPA, since the application can render and appear functional while it's fetching data.

Still, not sure how damage control for poor performance is a "pro" of serverless design.

Well, there's very little (if anything) that "serverless" can do that other techniques can't accomplish. It's about costs & benefits, not whether or not you can do something.

Though I tend to agree I'm yet to hear a really compelling description of why I should move very much into it. Some of this may be because I tend to write in a style that makes it fairly easy to mix & match bundles of application functionality anyhow, so to me adding some tiny function to a running app isn't that big a deal. (I don't use Erlang directly, but Erlang is where I learned this from.) If you're in an environment where deploying a single new REST handler or some recurring service is much harder, though, I could see where it comes in handy for certain things.