Swift is a nice language in its own right, and, according to the post, is a good fit for the lambda environments.

So there doesn’t need to be a direct connection to iOS to decide to use Swift for serverless function. A developer might just decide to use Swift for serverless functions.

(I can see the benefit to sharing certain kinds of code between client and server, but a lot of things have to line of for this to make sense, so I’m not sure if that’s a significant driver.)